Release Techniques - Timers

Wall Light Timer

The idea is that if you can not see the lock, you can not unlock it. This works really good with simple combination locks. Avoid cheap timers, or have a backup timer in case.

Day Light

Similar to the wall light timer, this one is self explanatory, just make sure that there is not a storm the next morning, might be a long, long night.

Hour hand

If you position the hands on a clock correctly and dangle the key on it, eventually the hand will turn and the key will fall. Besure to test this with your clock. A variation on this is to remove the hands and attach a film can to hold the key.