Sewn on both sides with wide fringes. Woven very thin, despite the pictures, thinner than I expected. I was able to glue it to the backing and then cut it. This dust is damn good and I trimmed it out using a Diamant Dremel under my workshop dust collection system along with a paint suit, respirator and safety goggles and gloves as suggested. The white suit was gone when I finished. Now you need to insert into the casts and pour resin over them. Strength, I'm not sure. Look, very good. I bought Twill because I needed details. It's narrow enough that I'm fine with it, a wider blade would be fine if I was laminating and building in something like a skateboard deck, but I do jewelry inserts. Would recommend as a fair amount of square inches for the cost.