SparkFun's Description of the Nomad MDF Waste Board (Qty 4)
Are you accidentally damaging your CNC while milling? By mounting these 8 inch by 8 inch wasteboards to your CNC you won’t have to worry about cutting through a piece of flat stock and ruining the mill table underneath! Essentially, let the inexpensive wasteboard take the damage rather than your expensive CNC mill.
These wasteboards come in packs of four, are made of ½ inch MDF (medium-density fibreboard), and have predrilled holes and countersinks to make it easy to mount right to your Nomad.