Material selection depends on where the sign is going and how long it is going to remain. Outdoor signs are produced with heavier-duty materials such as aluminum, acrylic, and high-density urethane (HDU), because these are weather-resistant and won’t deteriorate. Indoor signs are produced with PVC, glass, and wood in order to have a better, smoother finish. Vinyl is a multi-purpose material in window graphics, wall decals, and pop-up displays.