Replace lost keys for your heirloom piece with Restorers 5/16” x 5/16” Solid Brass Skeleton Key. Fitting a replacement key to a lock is a relatively simple process. First, determine whether or not the lock has a pin showing in the keyhole. If so, measure the pin diameter. If your lock does not have a pin showing, select one of our solid shank keys with a bit size closest to the size of your keyhole.