Once you install the bolt down kit it's easy to install a chock from the top side - such as in an enclosed trailer - without having to crawl underneath. All our chocks have holes or brackets for bolting them down, but the bolt down kit just makes it easy to attach and detach from the top side.
The threaded inserts (optional) make it easy to install the kit from the top side. This is helpful with Toy Haulers and other RV's or trailers that don't have easy access to the underneath side.
**Please specify that you need the inserts for top side mounting when ordering.