If you work wood sooner or later you will need to create an Octagon from a Square. Maybe you are preparing a table leg, creating a table top or maybe a lamp base. You may want to layout a picture or mirror frame. There are a multitude of projects where the octagon will come into use. There are also several ways to accomplish this task, the one I have included here is quick and accurate.
There is also information and animations on the Math Open Reference website.