Chrome Series Adjustable Right Angle Clamp
Gibraltar's SC-GCSAR is an augmented version of a traditional right angle clamp. The augmented part is an adjustable ratchet tilter that allows you to change the angle and positioning of the bar.
The drum key screw inside allows you to lock in the angle that you want once you find it. So instead of attaching a bar at a 90 degree angle, you can have it offset and attach it whatever angle you want.