In UV Mapper? I suppose you'd have to select many small square sections and assign them all to the same group, same material. In Rhino, there's a lasso tool which you use to draw a little ring around the area you want to select, but you can also do ctrl+click to select every individual polygon one at a time, or in combination with the lasso. It would be great if UV Mapper had such a feature, but UV Mapper Pro might, I suppose. What are you trying to do, Rose? --Mike