the only hard thing about using the lockers is remembering which one you had........
if you have a digital camera with you, take a pic of your locker so you know the number of it.then you can delete the pic once you get your stuff out of it.
if you don't have a camera, write the number on the park guide or on your palm of your hand.
that's what i do.
the lockers are very safe.
i have used them since they started them.