That article was in Mainline Modeler but I don't recall the issue and my copies are currently in storage. The tool works very well and depending on the angle you use, it will allow you to make any wi width grab iron in small or large increments. The shallower the angle the smaller the steps in width. You need two pieces of styrene. The first you cut in the shape of a (politically incorrect term coming) Christmas tree. The trunk becomes the handle. Overlay the branch area with the scribed siding styrene. Then deepen the scribe lines with either a knife or razor saw. One pass of a saw is usually all that is needed.
Rich Orr
Sometime back one of the magazines ran an article where a piece of sheet plastic with manufactured scribed slots (siding?) was cut in a triangular shape with the slots running parallel to the base of the triangle. Then, you pick the slot that matches the width that you need and lay a piece of wire in it and simply bend it over the edges of the plastic. Bingo, a grab iron. The taller the triangle combined with a narrow base gives you a LOT of slots which vary in length only slightly as you go from one slot to the next.
I built one of these for a zero cost using scraps from the plastic box and it works great.