A. If there is no walls under the roofing item:
A temporary roof which one does not intend in making it for it to be a tent to hover over what is underneath it, but rather only in order to use [this roof] for a certain use, such as for example placing the board of a table on its legs, then even though in doing so one makes a temporary roof this does not pose a problem being that one has no intent to make a tent.
Setting up a strainer with dregs: See Examples!
B. If there is walls/boards under the roofing item:
Placing or removing a covering from walls which were set up from before Shabbos, such as a typical vessel: See D below.
Setting up walls on Shabbos and then placing a hovering over it: If one also places temporary walls under this roof [even if it only has two legs which are boards parallel to each other], then this is similar to a tent and is forbidden to be done in its normal form which is [starting] from below to above, and rather [must be done from] above to below [which is] an irregular form.
The above restriction only applies if one has a use for the space being formed: When setting up barrels on top of each other, one [barrel] being placed on top of two,…. then he may not set up the lower barrels first and then place the upper one on them because the space that is created between [the two lower barrels] is similar to a tent which has two walls and a roof. Therefore it must be made in an irregular way from above to below. However it is permitted to stand two books parallel to each other and place a book over them even though that this forms a handbreadths worth of space under them as since one has no use for the space between them it is thus not at all similar to a tent which has its space used. However by [setting up] barrels [it is forbidden, because] one requires the space between the two barrels in order so the barrels not mold, as it is for this reason that he set them up in this way [that one barrel stands on two as opposed to on one].
Similarly by a bed [as will be explained in the examples], even if it only has two [legs which are] boards parallel to each other, [since] one has use for the space between them [such as] to use it to store ones footwear and the like, and it goes without saying if it has four [legs made of] boards like a box in which one can conceal his items just like in a box, [therefore one may not place the board on them regularly].
The above restriction only applies if the roofing was not attached to the walls from before Shabbos: Any temporary tent which one has no intention into making into a tent [the Sages] only prohibited spreading over walls which one [had already] set up under it on Shabbos if the roofing had not been attached on its walls from before Shabbos. However if [the roofing] had already been attached to them from before Shabbos but it was placed there folded, then it is permitted to spread it out and set it up on Shabbos.
The reason for this is: because it is not similar to making a tent since one is not doing anything as the roofing was already set up and prepared together with the walls from before Shabbos and it is just that one unfolds it on Shabbos and sits on it.
Placing a board, sheet or mattress on top of a bed frame:
A bed [made in the following manner] that its legs are made out of boards which are attached [to each other] like the walls of a box and on them one spreads [a mattress, such as] leather or places on them a board from on top to sleep on, then one may not first set up the legs and then place the hide or the board on them in the way that is done during the week, because this is similar to making a tent. Rather one is to first grasp the hide or the board in the air and afterwards places the legs underneath it, as this is not similar to making a tent being that it is not common to build [starting] from top to bottom.
A bed of only two wall legs: Similarly by a bed, even if it only has two [legs which are] boards parallel to each other, [one may not place the board on them regularly].
The reason for why an irregularity is needed is: [since] one has use for the space between the [two boards, such as] to use it to store ones footwear and the like, and it goes without saying if it has four [legs made of] boards like a box in which one can conceal his items just like in a box, [therefore one may not place the board on them regularly].
If the top of the bed is barred with rope: If this bed does not have placed on it leather or boards but is rather barred with ropes from above, then if there are three handbreadths between each rope, in which case we do not consider the ropes to be all attached, then it is forbidden to initially spread a sheet over it on Shabbos or place a pillow or blanket on it being that this is similar to making a tent. Similarly it is forbidden to remove the lower cloth that is on it being that this is similar to destroying a tent. [However it is permitted to have one people spread the sheet and another move the bed under the sheet, thus having the roof set up before the legs.]
If the top was partially covered from before Shabbos: [However] if it had a pillow or blanket or clothing spread on it from before Shabbos the amount of a handbreadth, then it is permitted to spread [it] on Shabbos over the entire bed being that doing so is simply adding to a temporary tent.
Beds with regular legs: All the above [restrictions] only apply to the type of bed that has walls, meaning that its legs are like the walls of a box, even if it does not have four walls but rather only two which are parallel to each other. However by our beds which their legs are not given the status of walls, it is permitted to initially set up [the legs] and afterwards place a beam on them. [Similarly] if it is [a bed that is] barred with ropes then it is allowed to initially spread a sheet over them on Shabbos even if there are three handbreadths between each rope.
The reason:  This does not involve [the prohibition of] making a tent because such a form of temporary tent which one has no intent in making a tent out of, the Sages did not prohibit unless it has walls under it which reach the ground, as then it is similar to a tent.
If the walls of the bed are within three handbreadths of the ground:  Regarding if the walls [of the bed] reach within three handbreadths of the ground, this will be explained in chapter 502 [in Magen Avraham Halacha 9].
Setting up barrels:
When setting up barrels on top of each other, one [barrel] being placed on top of two, he is to hold in his hand the upper [barrel] and set up the lower ones under it. However he may not set up the lower barrels first and then place the upper one on them because the space that is created between [the two lower barrels] is similar to a tent which has two walls and a roof. Therefore it must be made in an irregular way from above to below.
The Reason for this is because: by [setting up] barrels one requires the space between the two barrels in order so the barrels not mold, as it is for this reason that he set them up in this way [that one barrel stands on two as opposed to on one].
Setting up books: 
It is permitted to stand two books parallel to each other and place a book over them even though that this forms a handbreadths worth of space under them,
The Reason for this is: since one has no use for the space between them it is thus not at all similar to a tent which has its space used.
Setting up a table on its walled legs:
If one does not need the space [formed under an item] then it is not at all similar to making a tent, and it is thus permitted to set up the upper [item] over the lower [item which is the legs]. It is therefore permitted to set up the plank of a table on its legs despite it having walled legs which reach the ground from all four sides being that one does not need the space that is between them.
A folding chair:
For example a chair made from individual parts and when one wants to sit on it one opens it and spreads and stretches the leather [seating] and when one removes [the seat] he closes it up and has the leather fold, then it is permitted to initially open it on Shabbos even if it has walls under it.
The reason for this is: because it is not similar to making a tent since one is not doing anything as the roofing was already set up and prepared together with the walls from before Shabbos and it’s just that one unfolds it on Shabbos and sits on it.
Setting up a canopy:
Opening and closing a shelf: 
Similarly [for the above mentioned reason, it is allowed to open and close] a shelf which is attached to the wall which has books placed on it even if it has walls under it.
Setting up a strainer:
A strainer that has dregs in it: A strainer which is hung to hold the dregs to filter it [from liquids such as wine], in which one stretches its borders to all sides, this is considered like making a tent and is thus forbidden to move it and stretch it if it was hung with the dregs from before Shabbos.
The reason: Now even though that making a roofing without walls [under it] does not have the tent prohibition [when done without intent to form a tent, as explained in Halacha 9], nevertheless here it was prohibited in order so one not do so in the same way that he does during the week, as this is a belittlement of Shabbos.
Setting it up to place fruits on it or filter clean water: However it is permitted to move it and stretch it in order to place fruits on it or other matters, or even in order to filter with it clear wine and water, which is permitted to filter on Shabbos and does not contain any belittlement of Shabbos at all.
Examples which relate to setting up bonfires on Yom Tov:
Setting up a bon fire in a way that one does not transgress the Ohel prohibition: It is the common practice when making a large bon fire to make four rows of wood [each corresponding] to the four directions, similar to the four walls of a box, and they then place on the [walls of wood] wood above and it is similar to [making] a tent [which is forbidden]. Therefore one who desires to make [such a bonfire setup] on Yom Tov is not to first make the walls and then make over them the roof being that this is the way of building, and even a temporary building is forbidden on Yom Tov. Rather one person is to hold up in his hands in the air the upper woods which are to be used for the roof and then arrange the walls under them in order to change from the normal way done during the week.
Setting up a table in a way that one does not transgress the Ohel Prohibition: Similarly if one is setting up a wood like roof over two stones which are made like a wall, then he is to hold the wood with his hands in the air and afterwards arrange the stones under it [in order so he not make a temporary tent without an irregularity].
Setting up a pot in a way that one will not transgress the Ohel prohibition: Similarly one who places a pot over two stones is to hold the pot with his hands in the air and afterwards arrange the stones under it in order so he not make a temporary tent without an irregularity.
Roasting eggs in a way that one will not transgress the Ohel prohibitions: Similarly when one is roasting eggs [in their shell] and places one egg over two eggs and the fire is between the two eggs, then he is to hold the upper [egg] in his hand and place the lower [eggs] under it.
If one does not need the space under the bottom items: However the above only applies when one places fire between the lower [items] as in such a case one requires the space between them and it is thus similar to a tent of which too he needs the space that is under it. However if he does not need the space that is between them then it is not at all similar to making a tent, and it is thus permitted to set up the upper [item] over the lower [items].
It is permitted to initially set up a roofing when one has no intention to place it there for protection in the following cases:
- Temporary: In all cases it is forbidden to make a permanent hovering even if one does not intend on doing so for protection purposes. The below allowances only apply when one does so temporarily.
- It has less than two walls that reach the ground: If there aren’t two walls under the roofing then it may be set up in any which way.
- If it has two walls or more that reach the ground then it is permitted if any of the following apply:
- If one first hovers the roofing over the floor and then slides the walls under it.
- The roofing was already attached to the walls from before Shabbos, like a folding chair or table.
- It may be set up normally even with walls if there is absolutely no use for the space which the roofing is hovering over, such as forming a small tent with placing a horizontal book over two vertical books.
- If the walls had already been set up from before Shabbos, and the hole being covered is not as wide as the hole of a barrel. –See D below!
Examples: It is permitted to:
- Unfold a folding chair or table.
- Fold or unfold a wedding canopy that was attached to its poles before Shabbos
- To place a table on its legs if the legs are not formed as walls.
- Place a book horizontally over two books which are standing.
- Open and close a shelf which is attached to the wall
D. Making a roofing on walls which were set up from before Shabbos-Such as placing and removing the cover of a vessel:
Items with a hole less wide than the size of the top of a barrel:
It is permitted to place a pot on the mouth of a I oven on Shabbos, as explained in chapter 353 [Halacha 14], and this carries no “Tent” prohibition in [roofing] the space [within] the I due to that the walls of the I were made and set up already from before Shabbos [and thus is permitted because] the [Sages] did not prohibit making a temporary tent when it is done without intention to form a tent with exception to when one places walls below it on Shabbos as explained above. However this only applies to a pot placed on [the mouth of] a I [and the like which is small], however the [law by the] mouth of a barrel that existed back which was a lot wider than the mouth of the I will be explained next.
Items with a hole as wide as the top of a barrel:
A cloth which is spread on the mouth of a barrel in order to cover it should not be spread fully across its mouth as [doing so is making a] tent. Rather part of its mouth must be left uncovered.
If the barrel is full to the top: [However] this only applies if the barrel is not full to the top and is rather lacking [at least] a handbreadths [worth of liquid in] as in such a case when one spreads the cloth over its entire mouth it is similar to making a tent over the space of a handbreadth.
However if [it is full to the point that] it does not lack a handbreadths [worth of liquid] then it does not have the status of a tent, as any tent which does not have the space of a handbreadth [under it] is not considered a tent at all.
The reason why it is forbidden when not filled to the top: However when it has the space of a handbreadth under it, then although the walls that surround this space, which are the walls of the barrel, were already set up from before Shabbos, and thus [one would think that] it should not be prohibited due to the tent [prohibition] [to spread a cover fully over it], just like it is permitted to place a pot on the mouth of a I oven on Shabbos [as explained above], …..nevertheless it is not similar to a pot placed on [the mouth of] a I because the mouth of the barrels that existed back then was a lot wider than the mouth of the I, and thus when one covers its mouth it is similar to making a tent even though that its walls have already been made from before Shabbos.
Removing the cloth covering from the barrel: The same law applies [regarding removing the cloth from the barrel] that it is forbidden to remove [a cloth] covering which covers its entire mouth if it lacks a handbreadth [length] worth of liquid, because it is similar to destroying a tent.
The reason for why removing the cap of a barrel is nevertheless always allowed: This [cloth covering] is not similar to the cap [of a barrel] which is permitted to remove and replace [on Shabbos] as explained in chapter 314 [Halacha 14] being that the cap is modified for this use and its modification reflects on it that it is designated for this use, [and] therefore it does not appear like a tent. However when it is covered with a cloth then even if the cloth is designated for this [use], nevertheless [since] it has no modification which displays that it is designated for this [therefore it is similar to a tent].
The law by the covers of other vessels: This law applies as well for the cover of [all] other vessels which are very wide to the point of the wideness of the mouth of the barrels of those days.
There are opinions which say that the above was never prohibited by a barrel and the like but rather by a tub and the like which are much too wide.
The Final Ruling: 
One is to be stringent like the first opinion, although those that are lenient like the latter opinion are not to be rebuked being that there are opinions which say that the covering of vessels does not involve [the] tent [prohibition] at all even by vessels which are very wide.
It is only a problem to completely cover a vessel or remove its covering which completely covers it if:
- The vessel has an opening the size of a wide barrel.
- The cover is a material which is not self evident that it has been designated for covering with, such as a cloth.
- The vessel has at least a handbreadth worth of empty space below the cover. [Meaning that it is not filled beyond there.]
It is never prohibited to un-fully cover a vessel, or to remove the cover of a vessel which is not fully covered.
May one open or close a folding chair, table, bed, stroller, and crib on Shabbos?
May one place a mattress over his bed on Shabbos?
Yes. However if the bed has two “leg walls” which reach to the ground then it may only be done if there is a board lying in the area the mattress is to be placed on, or its surface is lined with metal or wood panels or springs which are within three handbreadths of each other. Otherwise one must first place the mattress over the area and then move the bed under it. 
May one add an extension to ones table on Shabbos?
Yes. It may be inserted even into its sockets which are found in the table for this purpose.
May one insert/remove a drawer into/from a desk or table?
The question involved in doing so is that in the process one forms a hovering over the space in the drawer. The following is the ruling.
Some Poskim rule that it is forbidden to do so if the space in the drawer is one handbreadths deep, being that one is making a roofing through doing so.
Other Poskim however rule that it is permitted, as the drawer is a recognizable insert to the table, and is thus similar to the allowance to cover a barrel with a recognizable cover. As well there is no prohibition in placing walls under a roofing [as will be explained in Halacha 5].
According to Admur it is completely permitted due to the above mentioned reasons.
If cabinet/table holds 40 Seah: Seemingly in such a case it is forbidden to enter the drawer. [Vetzaruch Iyun why no mention of this is made in Poskim which deal with this question! From their lack of mention, it seems that it is allowed in all cases in their opinion.]
May one insert or remove a ceiling tile on Shabbos?
Doing so is forbidden.
May one leave keys under a ceiling tile by lifting up the ceiling tile and placing it under?
This matter requires further analysis.
May one open or close a pool cover?
It is forbidden to completely close a pool with its cover, or undo its cover if it was completely covered, if there is a Tefach of space between the cover and the water. If however it is clearly evident to all that the pool cover is modified for this use then it is allowed.
May one undo a wedding canopy that was left open from before Shabbos?
Yes, unless the canopy is meant to be a permanent structure and remains there on permanent basis.
 Biur Halacha 315 “Mitah”; Ketzos Hashulchan 120 footnote 13. Vetzaruch Iyun why this option was not mentioned by Admur.
 There the Magen Avraham brings that the Beis Yosef and Rama [in Yorah Deah 371/4] rule that we do not say the concept of “levud” for a stringency. However the Magen Avraham himself questions this ruling and concludes that one should be stringent.
 502/6; 315/9 “such as for example placing the board of a table on its legs, then even though in doing so one makes a temporary roof this does not pose a problem being that one has no intent to make a tent.”
 Vetzaruch Iyun as if the canopy is meant for protection then it should be forbidden, as in the beginning of the Halacha Admur emphasizes the Heter to be only if doing so not for protection. [To note the Chazon Ish tries to prove from here that for protection is also allowed. However clearly one cannot say so in Admur.] Now if one is not doing so for protection, then why should it be forbidden to set up even initially on Shabbos, even if not attached before Shabbos, as it contains no walls. Perhaps however it refers to a canopy that as well contains walls. [So explains also Tehila Ledavid 315/8 after similar analysis.] An example of the above would be a wedding canopy that was set up before Shabbos and was not removed, may it be taken down.
 Shaareiy Tziyon 315/34 and so is implied from Admur
 Meaning that one does not remove it from the wall but simply lifts it up or down, similar to the top of a chest which opens from its hinges.
 315/9 and 11
 Halacha 12
 Halacha 19 Vetzaruch Iyun Gadol from the case of the bed.
 Piskeiy Teshuvos 315/7
 Pashut, as explained in Halacha 3C in the example of folding chairs.
 See above 3C, and Piskeiy Teshuvos 315/7
 Even if the walls of the bed, were set up from before Shabbos, nevertheless this condition would need to be met being that the hole which the mattress is placed on bed is as large as a tub.
Vetzaruch Iyun why in Piskeiy Teshuvos he depends the allowance of placing a mattress on the fact that its boards are within 3 handbreadths of each other when in truth this is only need by walled legs.
 Biur Halacha 315 “Mitah”; Ketzos Hashulchan 120 footnote 13. Vetzaruch Iyun why this option was not mentioned by Admur.
 Piskeiy Teshuvos 315/7; SSH”K 24/23
 Does this apply even if one plans to leave the attachment in for a long time, or only if he plans to remove it after Shabbos? May it be inserted strongly into its sockets? May one close a clamp over it?
Seemingly if it is only meant to be left there over Shabbos and then removed it is permitted even if it gets strongly attached. However perhaps we say that this allowance only applies by attachments that are not common at all to last even temporarily however attachments which are common to be left attached temporarily and it’s just that the owner does not plan to do so, then perhaps the allowance does not apply.
 Piskeiy Teshuvah 315/9
 Chayeh Adam brought in M”B 315/48. The M”B himself suspects for this opinion although brings that one who is lenient is not to be protested as they have upon whom to rely. SSH”K 24/24 rules like the stringent opinion.
 Ketzos Hashulchan 120 footnote 21; Kitzur Shulchan Aruch
 Ketzos Hashulchan ibid
 As although ceiling tiles are placed for mere beauty rather than protection, nevertheless since they are placed to be there permanently they are forbidden due to the building prohibition.
 Based on 2D above.
 This is forbidden according to all as stated above in D.
 As it is not made for protection and is thus not considered an Ohel.