"Danger - Propane, No Smoking" NFPA Sign By SmartSign | 7" x 10" Aluminum DURABLE ALUMINUM. Signs are made from heavy-duty, 40 mil thick aluminum. Unlike steel signs, our aluminum signs do not rust. Signs last up to 7 years outside. ROUNDED CORNERS. Signs have rounded corners and burr-free corners for safe handling, longer life and a professional appearance. LAMINATED. Graphics are protected from weather and abuse. Graffiti can be cleaned off. Laminated signs outlast competitive unlaminated or overcoated signs. EASY TO INSTALL. Signs have four 3/16" od corner holes. Mount with screws, nails, tie-wraps or wires. Signs can also be attached with foam or double-sided velcro tape. Sign attachment accessories are not included. SAFETY AWARENESS. Alert everyone to exercise caution while taking some burden off your shoulders, regarding safety on your property.