Shabbos 13:6-7

Shabbos 13:6

If a deer entered a house and a person locks it in, he is liable for trapping; if two people lock it in, they are exempt. If the house cannot be locked by one person and two people locked it, they are liable, though Rabbi Shimon says they are exempt.

Shabbos 13:7

If a person sat in the doorway but did not block it (so the deer could still escape) and a second sat next to him and blocked the exit, the first person is exempt and the second is liable. If the first person sat and blocked the exit and a second person came and sat next to him, the first is liable and the second is exempt. This is the case even if the first person gets up and leaves, leaving the second person blocking the door by himself. The situation is comparable to a person who locks his house for regular home security after a deer is already trapped inside.