An under-bed mounting system installed beneath a cargo bed floor of a vehicle includes both a male pin and a female receptacle. A releasable locking mechanism is defined between the pin and the receptacle to permit installation and removal of desired components such as a fifth wheel hitch. The pin including opposing first and second ends and an intermediate portion, a groove being disposed within said intermediate portion and including a stem and a base portion. A portion of the receptacle is received within said groove, selectively contacting said stem during installation and contacting at least the base portion after said installation. In one embodiment, the groove of the pin is generally L-shaped, the receptacle including a rod that is selectively received in the groove. In a second embodiment the pin is a scissor clamp with opposing jaws pivotable about a common hinge. The jaws engage the inner periphery of the receptacle.