This jig helps to find the center of a board for doweling.
Use it like shown in the Pictures. It can even be used with a drill press.
There are one stl file for 8mm drill bits and one for 6mm ones. The 8mm one will fit boards up to 30mm thickness and the 6mm one up to 25mm.
I strongly recommend using a bright color. It is much easier to find the part in your toolbox or even in the shop vac ;-)
If you are using ABS, witch I recommend, enable 'brim' to reduce warping.