I try to step on the scale at least once a week just to keep an eye on my weight. When working with designers on window treatments, I also keep an eye on the scale because even the best design using the most beautiful fabric can be ruined if the proportions are off.
I use Minutes Matter Studio software to make scale drawings. The most common question I am asked is how many widths of material (WOM) are needed for stationary drapery panels? The general rule is to make the panels look as if they are operable. You don't want the panel to look like a piece of spaghetti hanging at the side of the window. Nor do you want the panel stretched out almost flat so that it visually takes up more space. These are my recommendations.
Scale drawings also help with how long to make a valance and where to mount it on the wall. To my eye, the last valance best fits this window and wall configuration.
An innovative way to use scale drawings is to determine how to cut the fabric. Here is an example where I showed what a shawl valance would look like with the fabric cut up the bolt and how it would look with the fabric railroaded -- the client chose railroaded.
Bev Dyminski Interior Design
You know you've done it right when you compare your scale drawing to your finished product and it's hard to tell the difference! If you want to make sure your proportions are right and have your client ask "Is it live or is it Memorex?, contact me at firstname.lastname@example.org and we'll get on the scale together. To see more before and after examples, check out my Scale Drawings webpage.