The following Halachos relate to the Melacha of Boneh—building--and are excerpted from The Shabbos Home, Volume 2, by Rabbi Simcha Bunim Cohen, Shlita:
1. It is permitted to remove the sink strainer from the drain, and replace it there on Shabbos. Since the strainer is made to be removed and replaced, it is not part of the structure. Therefore, one who replaces it has not added to the structure. Similarly, child safety gates that fit into tracks attached to the wall are made to be removed and replaced; therefore, their insertion is not included in the Melacha of Boneh.
2. On the other hand, one is forbidden to replace a faucet handle on a sink even if it will be replaced loosely and will not be screwed on.
3. Similarly, it is forbidden to replace the wheel of a stroller or carriage on Shabbos; to reinsert the leg from a table or chair into its socket (even loosely); or to slide rubber or plastic caps onto the legs of chairs or tables.
4. It is forbidden to replace a doorknob on Shabbos, even if it is merely inserted into the door without being screwed in. However, one is permitted to insert a screwdriver (or other metal rod) into the hole of the doorknob, and use it to open the door.
5. If a Mezuzah fell off the doorpost, it may not be replaced on Shabbos. This refers both to the Mezuzah holder, and to replacing the Mezuzah itself within the holder.
Important Numbers
