Southern California archer Bruce Arnold must have thought sharpening 3 blade broadheads didn't make them sharp enough, so he added razor blades. He used injector blades which had a corner removed so the would fit on a broadhead. He must of had a fixture of some kind to get them as precise as he did. I imagine they were done with a grinder. Also, a jig must have been used to drill the holes in the heads. He installed them with what looks like Pliobond glue and brass eyelets. The Bodkin is just glued. I'm guessing these were done sometime in the late 1950s. The Hill's Hornets look like a later version.