here is the jig for shelf pin holes, it's adjustable for width, and those two black stepped pins are used to hold it in place after the first hole is drilled, so it doesn't shift as you go along, and to extend the holes beyond the reach of the jig. it's from Rockler. also, two shots of the special drill bit that comes with it. you can get either 1/4" drill bit version, or 5mm version (if you like metric stuff
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