the tumblers inside the lock barrel sieze up with not been used. if you lift open the flap and spray in wd40 then work the key backwards and forwards it will free it up.it may take 5 or 10 mins to get it working and keep spraying to get the dirt and rust out,using a different key to move the tumberlers to a new place a helps ,then the car key to move them back. one thing to remember is any ford key will lock it but only the right one will unlock it
bob
February 2012