May one lie on a hammock which is attached to a tree?[1]

If the hammock is directly attached to the tree in an area that is above 10 Tefach from the ground the hammock is forbidden to be used in all cases.[2] If the hammock is not directly attached to the tree but is rather attached to a metal pole or nail and the like which is attached to the tree, then it still remains prohibited to be used if doing so will cause the tree or its branches to shake in the process. If however no part of the tree will shake in the process of using the hammock then from the letter of the law it may be used.[3] However some Poskim[4] forbid its use entirely under the claim it is difficult to ascertain whether such action causes the tree to shake.
If the hammock is attached to the tree from below 10 Tefach to the ground, it may be used in all cases.[5]

May one use a swing which is attached to a tree?[6]

This maintains the same ruling as using a hammock. Hence:

If the swing is directly attached to the tree from above 10 Tefach from the ground it is forbidden to be used in all cases.[7] If it is attached to a metal pole and the like which is attached to the tree then it still remains forbidden to be used if doing so will cause the tree or its branches to shake in the process. If no part of the tree will shake then from the letter of the law it may be used.[8] However some Poskim[9] forbid its use entirely under the claim it is difficult to ascertain whether such action causes the tree to shake.
If the swing is attached to the tree from below 10 Tefach to the ground, it may be used in all cases.