Release weights are designed to assist in releasing a caught fish from deep water.  It is placed in the mouth and when the fish descends to a stabilizing level, it is released from the fish and the fish is allowed to go on it’s own.  It is attached to a separate rod and reel.  I like to have release weights on a separate rod and reel that is used only for that specific purpose.  This eliminates the need to have people who do not know what they are doing punching holes in a fish to release the bladder.