Tri-Lok Manufacturing manufactures high-security cylinders for elevators. The cylinders enable the removal of passengers trapped in stalled elevators. They also help those who service and repair elevators do their job. And they prevent unauthorized persons from using screw drivers, sticks or bent wires to open the elevator doors when it is not at a landing. Various industries use Tri-Lok locks, including apartment buildings, office buildings, prisons, hospitals and universities.