dave if it was in your van if would of slid forward and killed you by now!
the bottom frame is bolted down by 6 bolts through van floor with spreader plates.
the top 2 frames are bolted to the bottom frame and sit tight around the top of the tank.
the tank sits inside the frame.the frame is 2 inches thick made of steel.it cant jump up over the edge!
simple really.the frame is heavy as well.