For removably coupling a boat apparatus, such as a boat seat or table, to a boat deck, a base plate having a clamping slot is attached to the boat deck and the boat seat or table or the like is supported by a base assembly having a clamping bolt. The base assembly is placed over the base plate with the clamping bolt engaged in the clamping slot and a manually operable member on the base assembly is manually operated to releasably clamp the bolt securely in place in the associated slot.