40mil Magnetic Strip with Rounded Corners will hold up to repeated opening and closing of doors. Never worry about wasting precious seconds searching for keys and fumbling to lock a door. LOCKDOWN Magnetic Strips are a fast, easy, budget-friendly solution to help secure classrooms during a lockdown or emergency. We have designed effective lockdown magnetic strips printed with easy-to-use instructions which will allow teachers & substitute teachers to lock a classroom door lightning FAST without any keys! Easy 1-2-3 Instructions printed directly on the Lockdown magnetic Strip: Step 1) Lock the Door; Step 2) Cover the latch plate with LOCKDOWN Magnetic Strip; Step 3) Keep Door Locked, Open & Close Door with Magnetic Strip in place. During a Lockdown or Emergency, Simply Remove LOCKDOWN Magnetic Strip & Close Door. Consult with your school security team to ensure use of magnetic lockdown strips is permitted at your facility. One color per pack. Colors may vary. WARNING! – DO NOT USE LOCKDOWN MAGNETIC STRIPS ON FIRE DOORS OR EMERGENCY EXITS!