Tonneau capable bed rackrails?

Mounting System For Truck Bed Racks t slot truck bed rack Bed Rack for tonneau covers that have an integrated T Slot along the bed rail tusker on order awaiting build slot Smart System · The smarter way to customize your truck bed · Roof Racks · Drop Rack · Platform Rack · Roller Rack · Load Bars · Gullwing-Bins · Kitchen- Bin

the tweety house slot Question: There seems to be limited info on how these rails install Do they clamp to the bed rail or do they utilize the stake pockets?