This is a set of doweling jigs that I designed and have used successfully in a number of woodworking projects. Most of the bases (for tables and benches) that I create are made with 2x2 lumber (effectively 1.5"^2). These jigs work excellently along the edge of such a piece (in any orientation) and allow you to accurately drill out holes in the correct spots so that you can ultimately join your pieces together using wood glue and dowels.
I use them by affixing the jig with a clamp and once it is securely in place, using a drill to cut out the holes in the exactly correct spots.
The jig with only 1 wall can be used if you have a separate spacer. For example, you could cut a length of wood and use that to exactly space the jig some distance away and then clamp everything down. The tolerances are quite accurate so this has worked well for me during multiple projects.
Amazon Basic PETG
This did not work well with PLA. Too brittle. I strongly suggest using PETG for this.