BoatBuckle CargoBuckle Flush Mount Tie-Down System The CargoBuckle Flush Mount System enables the CargoBuckle to be instantly ready when you need it, but neatly tucked out of the way when you don't. To use, simply open the "trap-door" and the CargoBuckle hinges up to the ready position. When not in use, the CargoBuckle hinges below the floor and the "trap-door" closes.