A brand of flashspun high-density polyethylene fibers, a synthetic material; the name is a registered trademark of the DuPont company, well known for their production of chemicals and textiles. Tyvek is often used as housewrap, a synthetic material used to protect buildings during construction. The material is difficult to tear but can easily be cut with scissors or a knife. Water vapor can pass through Tyvek, but liquid water cannot. All of these properties make Tyvek useful in a variety of applications.