Mexican Hand Clamp

The act of transporting large objects (sheets of wood, mattresses, etc.) on the roof of one's car using only hand strength to retain the cargo.

Mexican Hand Clamp example:
Juan: Yo vato, we need to rent a truck to transport some plywood.
José: No esé, we'll just (Mexican) hand clamp that shit on my 94 Civic and drive reaalll slow.