Common sense would consider attaching a heavy load (sometimes as heavy as a travel trailer) to the frame of the truck and not the thin sheet metal truck box.  It's a lot like attaching your truck's trailer hitch to tow your 2,000 to 4,000 lb. boat to your sheet metal truck bed as opposed to the truck's frame.

This brings us to the next tie down system, Frame Mounted.  Here, the truck camper is attached directly to the truck's frame.  There are many styles and configurations of frame mount tie downs, as well, most of which are universal in nature, designed to work on many different truck makes and models.  Because of their universal design, in most, if not all, cases, there will be concessions made as far as ground clearance loss, unsightly appearance, and even non-effective tie down operation from having to locate the tie down in only limited locations on the truck frame, allowing excessive movement of the camper when in transport.

Often, due to varying truck models and designs, the universal frame tie down has less holding ability than required and can flex quite a bit, even to the point of contacting and damaging the truck body.  Universal frame mount tie downs will either clamp on (with J bolts) or require drilling of the vehicle frame.  It is important when tying down any camper to have a good angle of pull on the camper.  In other words, if the chain between the camper and tie down is plumb (vertical) or close to plumb, the camper is going to move.  There should be a minimum 7" offset (more is preferable) between the camper anchor and the tie down to increase this angle and hold the camper from shifting.  Remember, just because it says frame mounted doesn't mean it's going to do the job better.  Frame mounted is only better if it is installed correctly with correct offset angle on each tie down point, and is engineered to be strong enough to handle the load in your specific application.