T-slot, stake pocket or clamp: how bed racks attach
T-slot racks bolt into the rails of covers and bed systems that have T-slots; stake-pocket racks stand in the four pockets and sit above a low-profile cover; clamp racks grip the bed rail and generally block a cover; drill-in racks need holes in the rail. The rack's static and dynamic load ratings are separate figures and both are the maker's.
Cover and rack together
A cover line's rack support (T-slot rails, stake-pocket racks above the cover, none) is listed on its row in the tonneau tables; a rack's cover compatibility is on its row in the rack tables.