Indeed, Charly, that is quick and easy.
Bruce, as you can see, there are often several ways to get most things done in SketchUp. Charly's method is quick and easy. Although the methods Peter and I show are a little more involved, they would be useful in other situations as well. Miters on complex moldings would be one example. Charly's method only works if there's a face perpendicular to the miter cut. I can think of at least one more way to do it but I don't want to confuse you.