A word of warning. Make sure that the chock block can not come out of the holder while driving, and if it happens, that the chock block will not separate from the trailer/truck. One of my soldiers was driving a 5 ton on the Autobahn when that happened. The chock block bounced all over and then went through the windshield of a car following behind. The driver was killed and the ensuing wreck involved several other cars and injurys.