This is a toy bus that actually rolls. It prints as a frame, windows, bumpers, and wheels, so that it can be printed in three different colors of PLA. For this model, I used 8-32 philips-head machine screws (3/4" long), 12 washers, and 4 8-32 hex nuts to secure the wheels so that they roll. I put a drop of LocTite blue threadlock on the threads to keep the nuts from coming loose accidentally. The windows and bumpers were attached with superglue. It was designed for use in a brain-injury support group that is working on relearning life skills (such as riding a bus).