[olliecooper]

I haven't used the Makita set up, but I assume that it should be similar to the Festool. There is a mark on the side of the router base that represents the center of the collet. Put the rail down on the plywood. Put the router on the guide rail. Loosen the guide rails screws on the router base. Move the router in and out until the mark on the router base aligns with where you want the center of the dado to be. Tighten the guide rail screws on the router base. Set bit depth. Fire up the router. You made need multiple passes.