- Question: [Thursday, 16th Sivan 5781]
Dear Rabbi, we have a makeshift curtain that we constructed over our sliding door to shade from the sun in the afternoons and for privacy purposes and the way it works is that one side is nailed into the wall on one end of the sliding door and the other side has a nail that is punctured through the curtain and there is a hole that is made on the other side of the sliding door into which this nail with the curtain can be entered into. This nail that is attached to the curtain is meant for constant removal and insertion into the hole in the wall, as we see fit. My question is whether this may be done on Shabbos or is it considered like building being that I am inserting a nail into the wall?
You should not do so on Shabbos due to worry that you may come to make a bigger hole in the wall in the process in order so it remain firmly inside, as well as due to a rabbinical decree that the onlooker does not know your intent of removing it and hence it appears like building. Rather, simply nail in a permanent nail to that side of the wall and make a hole in the curtain which you can then hang onto the nail and remove. In all cases, when you place the curtain onto the nail you have to be careful that it does not hover a Tefach over the ground due to the Ohel prohibition, and thus you should first stretch it out fully [without any forward bends in the curtain] and only then hang it.
Explanation: Generally, inserting a nail into a wall on Shabbos consists of the biblical building prohibition [i.e. Boneh] while removing it consists of the destroying prohibition [i.e. Soser]. This applies even if the nail was only loosely attached to the wall. Nonetheless, this only applies if the nail is meant to last at least temporarily, while if it is meant for constant removal and insertion then it’s insertion and removal does not contain a building prohibition, and it is for this reason that the Poskim rule that a knife may be inserted and removed from a wall on Shabbos. Nonetheless, this only applies if the corresponding hole in the wall was made before Shabbos and the knife was inserted into it at least one time and then removed, otherwise we suspect that the removal can cause the hole to widen which would transgress the building prohibition. Now, seemingly we can apply the same rules regarding the above type of curtain nail, that if it was nailed in and removed once before Shabbos, then it is permitted to enter and remove on Shabbos as well so long as it does not make any more of a hole, being that it is meant for constant removal and insertion. However, in truth the cases are not the same, as everyone understands that a knife in a wall is meant for constant removal and insertion, in contrast to a nail which is commonly left inside a wall for permanent basis. Hence, while one can argue that there is no Biblical prohibition involved in doing the above on Shabbos, nonetheless there is room to learn that it would be rabbinically prohibited due to the fact that it appears like one is building. We find a similar concept brought in the Talmud and Poskim regarding pegs and bolts of a door that it does not suffice for them simply to be meant for constant opening and closing, which they are, but rather they must also contain a clear recognition that they are not meant to be nullified there, and hence seemingly the same would apply here. This applies even though the nail will only be loosely fit into the hole as nonetheless to the onlooker it may appear like building. Another possible concern with a nail is that one will push it in too deep and end up making a larger hole. [Another possible issue to raise in the above case is the fact that we find regarding other Halachas worry that one may come to leave the item there forever, and so too here perhaps one will choose to leave that side of the curtain there forever and rather open the other side. However, in truth this is not a worry at all, as whenever one side is already permanently fixed, we do not assume that one will come to change his mind regarding the other side.] Therefore, my conclusion is as above, that the above should not be done due to a possible rabbinical prohibition, and rather one should hammer a permanent nail into that side of the sliding door and make a hole in the curtain before Shabbos which he can then hang onto the permanent nail and remove it as he sees fit, as hanging a curtain on a nail does not contain any prohibition on Shabbos if one make sure that it does not hover a Tefach over the ground, which is beyond the scope of this explanation to elaborate on..
Sources: See regarding the Biblical prohibition against nailing a nail into the wall: Admur 314:2; See regarding the prohibition of removing an item from the hole for the first time and thereby widening the hole and the allowance to enter and remove a knife from a hole in the wall: Admur 314:4; Michaber 314:12; M”A 314:5; Taz 314:2; M”B 314:11; Regarding the law of pegs and bolts see: Admur 313:3; Regarding rabbinical decree against placing a nail into a hole even very loosely due to worry that one may come to put it in strongly, see: Ketzos Hashulchan 119 footnote 4; Regarding the worry that one may come to nullify one of the sides there, see: Admur 317:10; Regarding being careful that the curtain does not hover a Tefach over the floor, see: Admur 315:7; Rama 315:1; Michaber 315:12; Rambam 22:32