After the z-slider the belts go to the pulley. If you look on the underside of the Z-platform of the Promega, you will notice that two of the four belts cross over themselves. This allows the bed to be driven by a single motor with a single axle. The belt that crosses over is referred to as the Flipped Belt. Follow the section immediately below to route a bed as normal, and the section Flipped Belts to route the flipped belt. When facing the front of the Promega, the right side belts of the Z-platform should have its belts flipped.