In search of safe magnets to use in the classroom or in a children's environment? Hero Magnets to the rescue! Chunky size with magnets completely encased in plastic. Strong display magnets help you get, and stay, organized. Great for whiteboards, filing cabinets, fridges, and more. Big Block Magnets come in a box of 40 super-strong plastic-encased block magnets. Each Big Block magnet measures 2"L x 1"W x . 50"T and holds up 20 pieces of paper! Use # 2 - Lockdown Safety! Quick and easy to use in the event of an emergency lockdown! How to use: Open the door. Place a magnet on each door's lock plate or steel frame. Leave the magnet there at all times. Keep the door locked and open. (In non-emergencies, the magnet prevents the door from shutting and locking anyone out. ) In the event of a lockdown, simply remove the magnet and shut the door. It will lock immediately.