4mm Corrugated Plastic is a lightweight, inexpensive sign board that can be used outdoors. Often used with “H” frames, these signs are often used for political campaigns and other advertisements along roadsides and in front of stores to promote sales. The “flute” lines make for a less attractive interior sign-but these inexpensive signs are a step up from the “handwritten” poster, and are often used in shops to post company policies, shop rates and more. Outdoor durable. Included is our Arched Top Angle Iron frame. No hardware needed with these slide in frames! Sign slides in behind punched out scallops that hold the sign blank in securely.