It is only Biblically prohibited to tie or untie a knot if:
- At the time of making it one plans to let the knot remain tied for as long as it can possibly last and does not plan to ever untie it.
- According to some opinions there must also be fulfilled: That the knot is strong and tough similar to the knots that professionals make in their labor.
It is Rabinically forbidden to tie or untie any knot that:
- Is made in a professional manner even if not meant to last at all [even in a scenario that involves pain].
- Is meant to last temporarily, meaning that one has in mind a set time by when he will undo the knot, and this set time is past 24 hours from when the knot has been made.
- The knot is a type of knot that is at times left to last forever, then it is forbidden to tie it.
It is permitted to tie and untie any knot which is:
- Any knot which is only Rabbinically forbidden to tie and untie [i.e. any knot which one has a set date to untie] may be tied for the sake of a Mitzvah.
- If not needed for the sake of a Mitzvah then it is permitted if all the following conditions are fulfilled:
- The knot is not meant to last for 24 hours. In time of need if it is meant to last for 24 hours , but for less than 7 days, then one may tie or untie it through a gentile
- It is not a professional knot.
- The knot is never usually left to last forever.
- It is not the first time that this knot is being open or is but does not make a finishing touch to the vessel. If it does then it is forbidden due to Fixing a vessel.