I have a 10 degree wedge ruler that I extended. I had my brother cut the addition out of plexiglass. I laid the ruler on a sheet of paper and took a ruler and extended the lines of the ruler. He cut the wedge out of plexiglass. I use wide pacing tape and tape it on the end of the ruler when I need it. WOrks great. You just need to be a little careful when you cut past the seam in the ruler. If you arent careful it will catch on it.