This drill jig is perfect for drilling perfectly located 5/16" holes in your raft frame tubes. It sets the hole location perfectly to align with the hole in the frame clamp (universal between Revolver clamps, and NRS clamps).  The system improves when you use 2 jigs, set one on each end, lay on a flat surface, and both hole sets are as parallel as the surface you set them on.  

They are 3D printed, and inserted with 2 5/16" drill bushing.  One bushing at the top to and one in the center of the tube ensuring straight holes through both walls.  It accommodates standard 1.25 Schedule 40 or ~1-5/8" tube, which is the same size that NRS uses on all their frame parts.