Broken, stuck, and lost keys. If a key breaks in the lock, insert a coping-saw blade in the keyhole just above the key’s teeth. Hook onto the front of the key shaft and pull it out. If that fails, remove the lock cylinder.
Many locks let you push out the key by poking a stiff wire through the cylinder. If the break is deep inside, use a coping-saw blade to lift the front tumblers out of the way.
If a key is hard to turn, the lock may be clogged. Spray lock lubricant into the cylinder to flush it out. If necessary, disassemble the lock, soak the parts in a solvent, such as kerosene, and lubricate them sparingly.
Keep a list of the code numbers on your keys, especially auto keys. A locksmith can make a new key for any lock, but it costs less with the code.