A client wanted a "modular" for his busy board store. I created this as a prototype,, but the customer wasn't interested. Some features that aren't obvious: The drive wheel has indents instead of a knob that can catch on things; the axles are bolts with either tradition 'hex heads' or for more tamperproof(ness) trex head. The axles are mounted on metal inserts for better alignment and stability; and the axles are secured with a thread locking compond (loctite). Can't win them all.