The Rapid Lockdown Magnet secures classrooms in seconds without needing your keys. Place the Rapid LockdownMagnet over strike plate on metal door frame. Put door knob in locked position and close door. Then come and go freely. When lockdown occurs open door slightly, remove Rapid LockdownMagnet and close door. Door is already locked. Strongest lockdownmagnet on the market today--40 ml thick. Non-tearable. 9" tall by 1.75" wide. 50 Pack. America's #1 choice used in over 2,500 schools in all 50 States is the Rapid Lockdown Magnet for Faster & Safer School Lockdowns. 9" tall by 1.75" wide. Strongest Lockdown Magnet on the market today. 40 mil Thick. Non-tearable. Long Lasting. Meets the Dept. of Homeland Security's #1 recommendation to be able to quickly lockdown classroom doors without a key. Designed by a School District Security Director and Police. When EVERY SECOND COUNTS you can count on the Rapid LockdownMagnet.