If you have had the bed heater thermistor wires break off on your Mega-S like I have (twice), then you need this. It snaps under the Y carriage and keeps the heater wires secured in place so they don't flex when the bed moves back and forth.

Updated 11-5-19: Added a second piece that guides the wire coming from the base. This sends the wire up and back to keep it from snagging on the Y rod mounts and Y motor sprocket. Print it with the cutout side down. I had to use a brim.

Updated 11-9-19: Adjusted wire support to fit better on Y plate.