Often all you need to do is run a pencil lead (graphite) on your key
if there is a lubrication problem.

I recommend against using pencil lead as a lubricant. It *does* contain
graphite, but it also contains clay. (The amount of clay is what
determines the hardness.) The clay is abrasive and will not do good
things to the lock.

--
Steve Bell
New Life Home Improvement
Arlington, TX USA