12mm plywood for the side parts
6mm plywood for the base part
20mm round timber
rubber gaskets for hindering of timber cylinder
(26x18x4 mm in my case)
1) Cut two pieces of the base from 6mm plywood. Adjust the holes size for your round timber and gaskets.
2) Cut two pieces of side parts from 12mm plywood. Check the size of pocket
I have made the version "B". Because of my poor skills with Adobe Illustrator I had to combine SIDE and POCKET files during import. If it's difficult for you I believe that the version "A" will works.
3) Insert the rubber gaskets between two parts of base and glue them together.
4) Glue base with two sides.
5) Cut 6 pcs cylinders from timber.
6) Make some simple hammer.