"Bicycle Parking Only - Please Secure Your Bike Properly" Sign By SmartSign | 12" x 18" 3M Engineer Grade Reflective Aluminum Rigid design means your sign will never rust and resists wear. Sturdy surface / post mount signs are printed in color on a white background. Parking signs are printed with UV-stable ink, suitable for use at temperatures from -40 F to 180 F. Post this sign onto flat surfaces, posts and fences for a parking sign that can last for years.