An mat system with each mat having sloping lips which overlap with an adjacent mat's sloping lips and are secured by interlocking joints in the mats' lips and/or by captive locking pins to form an easily assembled and interconnected flat surface. In use, opposing ledges forms a slot within holes in the top overlapping lips to receive a captive locking pin. The pin is captive by mid body prongs which fix underneath the ledges in a mat's upper lip's holes, and the pin locks and unlocks with rotary turning of the pin resulting in the pin's keeper feet fixing underneath the similar ledges in the holes of the lower lip of an adjacent mat.