I didn't have any hex head bolts to assemble the Modular Stand, so I had to make my own knobs. These are sized for 5mm rounded hex drive screws. (The kind you commonly see on 3D printers). I thought I might need some glue, but the press-fit is plenty tight.

OpenSCAD included, in case you want to adjust for what you have on hand.

Flip the model X 180 degrees to print (hex opening at top) for an easy print.

Update: After some use I managed to shear off the interior pieces, so I hit the parts/screws with a drop of super glue gel. We'll see how that works. The screws I'm using are smooth heads -- some have knurls, which might work better.

Update: I set this to "work in progress" until I do extended testing with the glued knobs. Because there are few things more frustrating than failed parts.