I had an old bed frame with a few bent rails for the bed but also had a few that were in good condition and wanted to use it for rails in this rack.
Made the holes square and just a little bigger than i needed to allow for slight variations in pole dimensions. Also left the circle part which still allows for the EMT.
Also made it to use with the Honeycomb Storage wall system.
The square hole is 17.7mm x 17.7mm
The author remixed this model.
made the holes for the poles square to fit a pole that is about 15.5 mm square.