929. A Tree That Is Used as a Ladder

Eiruvin 3:7

If a palm is cut down and leaned from the ground to the top of the wall, the residents have the option to make a single eiruv; the means of entry between courtyards not need not be a permanent fixture. Similarly, the weight of a ladder makes it tantamount to a permanent fixture so it need not be attached. If the barrier between courtyards is made of straw, the residents may not make a single eiruv even if there are ladders on each side. This is because no one would use such unsupported ladders. If the ladders are in the center with straw on either side, then the residents have the option to make two eiruvs.

Eiruvin 3:8

If there is a tree on the side of the wall that it used as a ladder, the residents may make a single eiruv even though one may not climb a tree on Shabbos. Since this prohibition is only a sh'vus (i.e., to encourage rest) it does not preclude joining for an eiruv. If the tree that serves as a ladder is an asheira (a tree that is worshipped as an idol), the residents may not make a single eiruv because deriving any benefit from an asheira – including climbing it – is prohibited by the Torah.