A magnetic lock has different mechanism compared to all other house security devices. Majority of the magnetic locks work only if the electricity supply is available. You can opt for these locks if there is no shortage of electricity supply. On the other hand, manufacturers have also come up with magnetic locks which function for short time period without electricity supply. Sem Family Locksmith Minneapolis sells and installs the magnetic locks. We provide discount for the installation if you purchase the lock from us. A magnetic lock is most commonly used at patio door.