A simple bracket end designed to use wood dowelling as the rails between the bracket ends.  The bracket has fixing hole at top and holes for pins to fix dowels in place although glue will work equally as well.

The model is parametric allowing adjustment of Internal Width, Dowel Size, Base Dowel Number and Dowell Hole Depth

Other dimensions could be made parametric if required-let me know.

In its current setup it is 100mm between uprights and has 3 base dowels.