I designed a dowel jig / drill guide to easily drill fitting holes for a butt joint of 7 x 7 cm squared timber to build a solid frame.
I included tunnels so the sawdust can fall way and you can see markings on the wood for each row of holes and the center.
 

Besides what you print, you need 8 x 608-ZZ bearings (outer diameter 22 mm, inner diameter 8 mm, height 7 mm).

The spacer for in between the bearings is included in the print. 

Just insert bearing-spacer-bearing in each hole and you are ready to go.

Depending on your print, you might need to glue everything in place.

I plan to design also a more modular version of this, but this has to wait until my current woodworking project is finished. 

If you like it - leave me a boost or comment. 

Let's see how this can be optimised.