Drop objects in Port-a-brig and Port-a-medbay and it's gone.

[Coolguye]

Also I think the larger reason the Port-a-brig is never used is because few people understand how to properly use it. Even on the SA thread there were a few people complaining that it was useless because captives could just walk out and escape, not knowing that you were supposed to lock the fucking thing with your ID.