Unbound materials, usually single-sheet items, need to be attached securely to the mounts, unless matted or encapsulated. Metal fasteners, pins, screws, and thumbtacks should not come in direct contact with any exhibit items. Instead, photo corners, polyethylene, or polyester film straps may hold the object to the support. Objects may also be encapsulated in polyester film, though old and untreated acidic papers should be professionally deacidified before encapsulation. Avoid potential slippage during encapsulation – when possible, use ultrasonic or heat seals. For objects that need to be hung (and that may require more protection than lightweight polyester film), matting would be an effective alternative.