Think of square box wire screened rabbit trap with one end door in slide that is straight up and slides freely in slot. The SPST switch is treadle trigger of bark or wood the animal steps on in bottom of trap going to get bait at back of trap. When steeped on and closed 1/2 brass switch with contact points (SPDT in simulator).
When switch is closed, the #32 gauge iron wire ( where lamp is) that is holding the trap door burns in two and the dowel in bottom of trap door is free to fall shutting the opening of the box trap.
