Anyone that has ever looked at the sharp edge of a piece of .032-inch aluminum that serves as the glareshield for many metal airplanes has probably tried to think of a way to soften it up—for both aesthetic and safety purposes. While there are products available that you can apply to the edge, many builders are looking for a DIY solution. Soft fuel line or nylon tubing are good options, but how do you put a nice straight slit in the tubing?
The answer is a simple jig made out of hardwood, like oak. Simply drill a hole in a convenient board, close enough to the edge that you can cut a slit from the edge of the wood to the hole. The slit should be narrow enough to hold a razor blade.
Mount the jig in your vise and feed the tubing through the hole, with the razor blade wedged tightly in the slot. Be sure not to twist the tubing as you pull it through the hole. The result will be a nice straight slot that you can use to slip the tubing onto the edge of the glareshield.