[(E)]

After a discussion on the gurps discord channel I was wondering what are some mundane protections locksmiths can put in place to counter the magic spell "lockmaster". Thieves after all invest considerable effort in the ability to get past a lock. Having mages being able to cast a spell to bypass a lock makes things a bit unfair on the thief.
Some of the ideas discussed where
- having parts of the lock made from meteor iron.
- Multiple "fake" locks, forcing the mage to spend more ER/FP
- locks that can only be opened by magic that contain a trap
- placing a simple self locking "drop bar" to protect the main lock

What other ideas does everyone have?