Jamsill Guard is an adjustable sill pan flashing for exterior doors and windows, designed to prevent water damage from window and door leaks. Jamsill Guard is injection molded and extruded from high impact ABS plastics that do not facilitate thermal transfer and will not deteriorate or corrode over time. Jamsill Guard's simple design is inexpensive, easy to install, and more user friendly than other sill pans on the market. Jamsill Guard's multiple piece, telescoping design allows the installer on-site adjustability, to fit all rough openings and is bonded together in the field with PVC cement.