The gym allows customers to voluntarily return their keys. Typesetting can be used at the front desk of the gym, which means please borrow the key and return it to the front desk in time. The customer didn't return the key because he forgot to return it. The front desk of the gym used typesetting to remind everyone to return the key in time, thus putting an end to the phenomenon of returning the key overnight. So the gym allows customers to voluntarily return their keys. You can use typesetting at the front desk of the gym to indicate that you want to borrow the key and return it to the front desk in time.