This system includes a 3d file (sorry I didn't clean it up, don't critique my modeling!) The last design has a locking groove to lock the hooks in place. It works really really well.
All you need is a ¾" plywood cleat with a 45 deg cut on one end and a groove cut on the other end. I modeled it based on my cleats but there should be a parameter to change the cleat width. Mine was roughly 3" or slightly under.
Please make more hook types, I want to see what ideas everyone else has. Currently I have:
Ideas and alternates for locking groove
The ¼" groove is easy to mill with a table saw or router, but you may wish to use a 45 deg slot (triangular) to eliminate supports on this piece. Please community, make this better than what I have.
The author hasn't provided the model origin yet.