The Terawatt Industries Universal Y-Axis Plate mounts the heated build platform (HBP) to the y-axis smooth rods. With this design only a single plate is needed on the y-axis.  However, the Universal Y-Plate also works as a "heatbed plate" - where a second, smaller plate sits underneath it and acts as a y-axis carriage.  Terawatt fulfills this open-source product in T-6061 aluminum, but we also have a lasercut version introduced in 2013.