Timber ribbing/ridging tool

[Frank S]

Not sure if I am thinking about the same thing you are but the only machine I ever heard of or saw that cut a series of groves in the surface of decking boards was a hand planer or a walk behind floor planer instead of having the standard planning knives they were re ground to have 1 inch gaps leaving about 3/8" of the knives for the cutting edges. this may or may not be what you are thinking