If you have concerns about your spare tire lock getting rusty from getting soaked with water try this. Squirt a little non rust lubricant into the key slot. Then cut a small plug to cover up the key hole out of a soft plastic lid. Once you have a good fit, smooth some clear sealant over the plastic and the edge of the key hole to seal out the water. Then if you need the spare just peel away the sealant and it comes out with the plug leaving clean access to the lock.