"Reserved Parking" Federal Handicap Parking Sign By SmartSign | 12" x 18" 3M Engineer Grade Reflective Aluminum 3M AUTHORIZED. Signs use 3M reflective Engineer Grade film mounted to 63 mil thick aluminum. This assures that signs are durable outside. DURABILITY. 7-year durability backed by a 3M warranty and rustproof aluminum. ORIGINAL DESIGN. After countless and actual field testing of durability, plus years of customer feedback, we have confidence that our signs out-perform and outlast others. With so many counterfeits of uncertain quality, it is easy to get overwhelmed with too many choices. Buy the original. ROUNDED CORNERS. Signs have rounded corners and burr-free corners for safe handling, longer life and a professional appearance. INSTALLATION. Most signs come with pre-punched and pre-cleared mounting holes for easy installation. Signs mount to U-channel posts, square or round galvanized posts, wooden posts and chain link fences.