Square Double Cylinder Deadbolt Double Cylinder: A double cylinder lock is keyed on both sides of the door and is only locked and unlocked via a key. Often times they are used on doors where glass is near the door that could be easily broken and the thumbturn on a standard single cylinder lock would be accessible. Note: Some images of this product may be of single cylinder version of the lock with a thumbturn on the interior rather than a keyed cylinder. Caution: Double Cylinder locks can pose a safety hazard in times of emergency due to requiring a key to unlock. Please check local codes before installing. Baldwin was born in America, and in the spirit of its birthplace, strives constantly to achieve a rich combination of Timeless Craftsmanship and timely good taste. For more than 50 years, Baldwin has successfully aimed at setting new standards of excellence in its products for the home and workplace. The double cylinder function locks and unlocks on both sides with a key only. Finishes match those of other Baldwin products for unity of design. Polished and Finished By Hand! Manufactured using solid forged Brass for maximum strength and Security. Baldwin products feature the highest quality and craftsmanship that has been respected for generations.