How to Build a Metal Lock Box

Purchase a military-issue ammunition box. Expect these boxes to range from 10 to 18 inches long and 6 to 8 inches wide. Look for an ammunition canister with a rubber sealer around the inside of the lid if you want the lock box to be waterproof.

Place the lock box on a flat surface. Center a hinge hasp designed for locking gates in the middle of the front side of the ammunition canister. Mark the four holes in the hinge hasp on the canister with a pencil. Close the lid with the hasp taped to the side to make sure the hasp position facilitates air-tight lid closure.

Drill four 10 mm holes into the side of the canister with a 12 to 15 mm metal drill bit at the marked spots. Place the hinge hasp back on the side of the canister and thread four 10 mm bolts through the holes to secure the hasp to the outside front of the lock box. Apply a thin layer of silicone caulking to the tops of four nuts. Thread the nuts onto the bolts on the inside of the canister to hold the bolts in place and create a waterproof seal.

Close the canister lid and secure it shut by threading a key or combination lock through the hole in the hinge hasp. Open the lock and fill the new lock box with important items. Lock the lock box and store it in a cool, dry place. Elevate the lock box if you have children and are concerned about them finding and trying to open the lock box.