This kit is for use on the RV-3, RV-4, & RV-6 kits (before pre-punched kits) to build the horizontal & vertical stabilizers in a jig.  Before pre-punched kits all the parts had to be built in a jig and the holes drilled while everything was held in alignment.  These brackets are mounted to a wooden jig and hold everything in alignment.   Six angle brackets are precision machined for perfect alignment of the hinge points.   The hinge bushings are machined bushings with a small hole thru the center of each bushing.  These are used to pull a small string or wire thru the bracket holes to align all the brackets on the jig.