Closed sockets are formed in the lower surface of a vehicle floor cover, such as a mat or tray. Each socket is adapted to receive a vehicle floor cover retention device which stands up from the floor of the vehicle foot well in which the floor cover is being installed. The sidewall of the body of each device acts as a physical stop to the sidewall of a respective socket, preventing or mitigating movement of the floor cover within the foot well. The top surface of the device may have a first fastener which is adapted to engage a second fastener on the ceiling of the socket. The device may be an adapter which is fastened to preexisting OEM mat retention structure. Embodiments of the adapter include one assembled from two pieces around an OEM retention post with an enlarged head.