A locker, a small, narrow storage compartment grouped together in dedicated cabinets with large numbers of similar lockers in various public places for the convenience of visitors to public places such as clubs, schools and public areas of a large buildings a factories and large firms.
Those specialized gym lockers I found when I visited a fitness club is very interesting. The key to an opened locker cannot be taken out of the keyhole until you put a 50 cent coin into a specialized slot on the inside of the locker door. After you have put the coin into the slot, you can then lock your gym stuff into the locker and do your thing in the club.
The great thing is in order to get back that 50 cent coin, you must insert the key into the keyhole and open the locker door. That coin is thus an incentive for the visitor to always return the key back to the correct locker before leaving the gym. This is a great feature for the administrators of the gym.