If the due date arrives and no payment has been made, the storage facility staff will send another notice and try to contact the customer by phone to remind them that they have a short grace period in which to make the payment before a late fee will be added. Once the late fee has been added, it is rather standard that the customer is no longer allowed to have access to the contents of the storage unit until everything is paid in full. The customer's key code for the gate to the facility will be deactivated and an additional lock will be placed on the unit. The storage facility manager does this so that they can be assured their payment instead of the customer moving everything out and not paying the bill.
Even after the self storage unit that is delinquent in payments has been locked down, there is still time for the customer to pay the monthly rent and all late fees. This amount of time varies among self storage companies, but it is written down in the paperwork that is given to the customer. At the end of the time period, the contents of the unit will be auctioned off. If there is more than one delinquent unit, the facility staff will choose a date to accommodate the waiting period for all of them to be auctioned on the same date.