In America, there’s a type of cover to protect one from accidentally turning on a wall light switch. It has two snaps that attach to the light switch plate on the wall, one on bottom and one on top.
In the event that one forgot to snap on the cover before shabbos, can it be done on shabbos?
It is controversial if it is considered boneh or not. Due to this, the opinion of R’ Shmuel Felder shlit”a is that essentially we should not attach it on shabbos, but if one does he has what to rely on.