Many years ago, I went to The Woodworking Show in Columbus, Ohio and bought this Dowel Crafter jig after seeing it being demonstrated.
I can count on my hand how many times I used it over the decades. There’s really nothing wrong with it, I just never got excited about dowel joinery.
The concept is simple. You draw a line on two mating boards and use it as a guide for the jig. You mark one piece “X”and the other piece “O”.
You then line up your mark with one of the alphabet letters on the jig and clamp it down. Then you flip it over and drill your holes through the circular black guides. The two guides spin and lock in place with a nut depending on how big of a dowel you’re using. Once you drill your “X” hole you repeat the process for the “O” hole.
You now have four holes that correspond with eachother. Next you can either use dowels or in my case, make a dowel with my Stanley No77 Dowel Making machine. I then cut the dowels and punch them through my Lie Nielsen Dowel Plate so they are the perfect diameter. When sticking them in the holes, they line up perfectly, giving me a nice tight fitting and strong joint.
This jig can also make dowelled miter cuts but you have to do it bass-ackwards. You first take your two pieces and mark your line. Then you drill your holes just as before. The jig had plastic 90 degree dowels you could buy as a kit. You can see how many plastic dowels I have used over the past 35 years.
After the holes are drilled, you cut your 45’s on the miter box and glue them together. The joint is remarkably strong. By far the strongest miter joint I’ve ever made.
You can buy this jig on eBay for about $20 but good luck finding the 90 degree plastic dowels. I love using this jig so much that I went out and bought a Festool Domino. Go figure. I hate dowel joints!