PTFE thread seal tape, commonly known as plumber's tape, is a polytetrafluoroethylene (PTFE) film used extensively in plumbing to seal pipe threads. The tape acts as a deformable filler and lubricant, allowing for a deeper seating of the threads and helping to prevent leaks in pipes by providing a watertight seal. It's typically wrapped around the threads in the same direction that the male threads are tightened.