I took the ones from the inventables grab cad site and modified these to work with the larger extruded aluminum which allows me to attach things to the legs and edges.
I used my 3d printer to make them.
Thought I would share how good these things work.
Those are great for tying cables to.
I made these to ziptie my power outlet / strip
They are wide enough to encompass the one I have.
Its very sturdy as I can plug things in and pull them if if need be easily and it does not move.
The one I made does not require any fasteners. It inserts in and you turn it to secure it.
You’re not alone - The initial pics don’t show that there are holes all the way through. I didn’t get it either. 
Sorry for the confusion but Inventalbes has these for the new systems they sell. Its in the cad file. I did mention I got them from there.
