"Caution - Low Overhead Clearance" Sign By SmartSign | 5" 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 pre-punched and pre-cleared 3/16" od corner holes. Mount with screws, nails, tie-wraps or wires. 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.