From Pixelmon Wiki
A trade monitor is the head piece of a trade machine. When crafted with a trade panel, a trade holder left, and a trade holder right, a trade machine can be created.
|Trade Monitor||Aluminum Ingot +
|Trade Machine||Trade Monitor +
Trade Holder Left +
Trade Panel +
Trade Holder Right
Prior to 9.0.1, Aluminum Plates were used instead of Aluminum Ingots in the recipe.