A friend’s roof rack needed some way to hold the ladders and other long things and keep them contained within the footprint of the vehicle. These stops were developed to keep things from sliding off sideways. The clamps are close fitting to the roof rack rail extrusion and have a key that engages the T-Slot on the top. The bolts pull the two halves together to form a clamp around the extrusion. The hex nuts are trapped in the bottom half so only an allen wrench is required to tighten the clamps.  Extra grooves and ribbing make the clamps very sturdy beyond the typical honeycomb core. The design is an original and modeled with SolidWorks. Extra rings on the protrusion of the stop allow for bungee cords or ropes or hooks to help fastening to the rack.