Heavy-duty low-profile adjustable-height floor locks have zinc-plated cast steel bodies and are stronger and more abrasion resistant than general purpose floor locks. They also have a lower profile than other styles of floor locks, which helps ensure sufficient ground clearance when the locks are used on low-profile carts. The locks' adjustable-height friction pads allow them to be used with casters in a range of heights. The height of the pads can be adjusted as the pads wear over time to help maintain proper locking and unlocking action. The bottoms of the friction pads have suction cups for increased grip. The locks have a top mounting plate for attaching them to carts and other equipment.