A very helpful accessory with fine adjustment for the OF1400 router. When you get it, you have to adjust some screws to make sure it fits tight to the rib on the guide rail. This is easy. Besides the guide rail use, you can also use it when doing freehand routing as a sort of base extension to keep the router from tipping, since the base of it is perfectly flush with the base of the router. With my router, I bought this and the fence. JD's shipping was amazingly fast!