PDO threads fall into two categories: non-barbed and barbed: The “Non-barbed” threads can be either smooth (monofilament) or braided threads. Non-barbed threads are mainly used to reduce wrinkles and lines on the face. Threads with barbs (or barbed thread) are thicker. Barbs hook under the skin and hold the tissue in place. When a barbed thread is inserted, it acts as an umbrella to support tissues that are sagging.