Placard holders display DOT (Department of Transportation) vehicle placards and NFPA (National Fire Protection Association) placards. They are installed outside of areas that store hazardous materials and on trucks that transport those materials. Placard holders are made out of durable aluminum. Their slide-in design allows placards to be changed easily to reflect current safety hazards. They also have a low-profile, split design for use on roll-up door panels.