Description: Part of a design for my filament holder, it's just a simple block that can be modified to hold different sizes of dowels.
Play around with the settings in the scad file to figure out how they respond. A basic rundown:
Rod_diameter: The exact size of your dowel. The script adds in 3mm of play.
holder_protrusion: The amount of distance the "U" protrudes from the face of the base
b_height: If you'd like a taller base to give you more 'gripping' area to drill/glue, make this larger than 0.
p_width: This is the thickness of the U itself. It is set at 5mm, which is thick enough to hold quite a bit of rod. Can set this thinner or thicker as desired.