We did ours with two self closing hinges. Doesn't need a catch. Hasn't come open in many miles and very rough roads. It isn't warm under there. As you can see, it is carpeted. There is an electrical junction box (closed up) at the very back. It is a great place for trays, cookie sheets, etc. Took us about 1/2 hour.
Happy trails......................
Sue and Ed Rowe
Hemet California
2005 3400RL
2006 GMC 3500 Dually, D/A, Crew Cab, Long Bed