To start cutting molding lines on a forestock I have used the technique of drawing a nice straight pencil line, following that with a veiner, and then straightening with a file, checkering tool, etc. They all work and all have their utility but all of them rely on getting the first line nice and straight. Quite some time ago now I stumbled on these two videos about an easy way to make a "beading" tool:
So when I saw the above links I thought, wow, that might be an easy way to get that first straight groove in place easily. So I made this very complicated tool:
And then ran it up and down the ram rod channel lips on a rifle.....like this.....
I used it first as a marking gage with just the smooth edge of the screw indenting a line in the maple. Then I turned it so that the screw slot actually cut wood. I have to tell you, that was the quickest, easiest, most sure fire way I have put a very straight groove in the forestock without fighting the grain or the natural wobble of the other tools / methods I tried. Once the initial line is establish, the rest os fairly straight forward....