Adjusting for height is easy. You can even scribe arches up to 16 feet wide. Laying out a segmental arch across an opening can be time-consuming if you don't already know the radius or have a fixed point to work from. You could calculate it from the height of the arch and the width of the opening, but that's not the kind of math most carpenters remember off the top of their head, and the trial-and-error method can be costly. If you find yourself needing to lay out these arches from time to time, or if you would like to, you might want to take a look at the E-Z Arch (E-Z Components, 3838 Raymert