This is a really simple bracket for joining 5mm plywood. I made a standing desk using these and some cheap 5mm plywood. it held together pretty well for several weeks. I glued the brackets and now its rock solid. you could easy change the design to allow for small bolts or something like that which would allow you to take the piece apart and flat pack it. could do a 3 way and use these to make cheap shelves etc. I would estimate the price at about $10. I included the file for the pen holder as well