About 40 years ago I read that William Proxmire, US Senator from Wisconsin, had a desk built for him that allowed him to stand while working. After commenting about Proxmire and his desk on another Instructable related to weight loss, someone suggested I do an Instructable on building a stand up desk. There are already several published Instructables related to stand up desks, and they will certainly be displayed in the Related Instructables at the far right of this Instructable's pages.
Here is an article on why sitting at a desk hours at a time is not healthful and why a stand up desk is better.
Step 1: Tools and materials
For tools I used sawhorses, a 7 1/4 inch circular saw, a measure, a square, a straight edge, "C" clamps, a drill, a screwdriver, and a pencil. I also made use of something I built in another Instructable to assist in cutting stock with a circular saw. (I did modify it and will mention the additions to it when that part of this Instructable comes.)
Pictured is the shelving on my sawhorses. Note the text boxes for layout instructions. Make a pencil line. This line provides a gentle slope to the top of the desk that makes reading and writing on the desk more natural. By making this angle cut about a dozen inches inward from the end of the shelf, I can cut once and the same angle will be on both upright pieces.