An L shaped bracket that is to be used with the standard "Large Size" Command Strips. 
The exact size are the 3.65" long Command Strips.

It should sit flush with the strips and is sturdy enough to hold a few sketchbooks from my testing. Please let me know if the commands if you decide to try heavier weight on it. 
 

General Print Guidelines:
Printed at 0.2mm layer height with supports touching base plate only. 

If your printer is tuned enough it should be able to handle the overhang of the hook without further supports. 

Please view the reference photo in the slicer for orientation.