never use wd-40 on a lock it can damage the springs and tublars instead go to the hardware store and get some of that graphite lock grease it usually is in a little tube for a couple a buck and it has a really thin little applicator so you can put it in the lock all the way to make sure it is lubed all the way

works great and its water proof if you damage the springs and tumblers or pins one could jam and then you will never gt it open again