Corbin Russwin ML2051 NSA Entrance or Office Mortise Lock, NS Lever, A Rose

The entrance function is the most specified function in any commercial mortise lock program. It's the lock on the office entry door, the school wing entry, the hospital department corridor, and the hotel suite: outside lever normally free, push-button toggle locks it after hours, key from outside unlocks when toggled, inside lever always free. The Corbin Russwin ML2051 NSA is that function in the ML2000 Series, ANSI F04, configured with the Newport (NS) lever and A round rose. It's Grade 1, UL Listed for 3-hour fire-rated doors, backed by a 10-year limited warranty, and built into a heavy-gauge steel lockbody with both a latchbolt and a 1" stainless steel deadbolt in the same mortise prep.

That last point matters on a specification level. The ML2051 provides life safety and security from a single door prep, eliminating the need for a separate auxiliary deadlock above or below the primary lock. For the complete ML2000 Series function lineup, browse Corbin Russwin ML2000 Series. For all commercial mortise locks, view our commercial mortise locks catalog.

How ANSI F04 Entrance Function Works

The toggle-action stop button on the inside controls the outside lever. When the stop is not engaged, the outside lever is free and the latch bolt retracts normally from either side. When the stop is pushed in, the outside lever locks out. The latch bolt can only be retracted from outside using a key in the cylinder. Inside lever is always free at all times regardless of toggle status, providing immediate egress without any unlocking step. Releasing the toggle can be done by turning the inside lever or by key from outside. This is the correct function for doors that need to be freely accessible during business hours and key-controlled after hours, without the complication of a separate deadbolt throw.

Corbin Russwin ML2051 NSA Technical Specifications

Series: ML2000. ANSI function: F04, Entrance or Office. ANSI/BHMA standard: A156.13, Series 1000, Operational and Security Grade 1. ADA: meets A117.1 Accessibility Code. Federal: meets FF-H-106C. UL/ULC Listed: UL10C positive pressure compliant. Fire rating: 3-hour A label, 4' x 10' single or 8' x 10' pair. California State Fire Marshal: approved. Windstorm/Hurricane Certified: yes. Buy American Act qualified. Lever: Newport (NS). Rose: A round rose. Handing: handed, quick reversible. Lockcase: heavy-gauge steel, 5-7/8" x 4" x 15/16". Front: heavy-gauge steel, 8" x 1-1/4" x 3/32"; accommodates flat and beveled doors (1/8" bevel in 2"). Armored front: wrought brass, bronze, or stainless steel, attached by machine screws. Latchbolt: 2-piece mechanical with anti-friction insert, 5/8" x 1" x 3/4" throw. Auxiliary latchbolt: 9/16" effective throw, 3/8" effective deadlocking. Deadbolt: one-piece stainless steel, 19/32" x 1-1/4" x 1" throw. Hub: steel, 5/16". C-to-C knob/lever to cylinder: 3-5/8". C-to-C knob/lever to thumbturn: 2-7/16". Backset: 2-3/4" standard. Door thickness: 1-3/4" standard (range 1-3/8" to 4"). Strike: ANSI straight lip, 4-7/8" x 1-1/4" x 1-1/8" lip to center. Cylinder: 6-pin, L4 keyway, brass standard; optional IC and security cylinders available. Keys: 2 nickel silver standard. Warranty: 10-year limited.

Auxiliary Latchbolt and Deadbolt: What They Do

Two separate security mechanisms operate inside the ML2051 lockcase. The auxiliary latchbolt is a small plunger that automatically deadlocks the main latch bolt the moment the door closes, preventing the latch from being retracted by shimming or carding. The deadbolt is a full 1" one-piece stainless steel bolt that provides positive security independent of the latch. Having both in a single mortise body is the argument for specifying mortise over cylindrical on a commercial entrance: the cylindrical lock typically provides one of these, the mortise provides both in one door prep.

Cylinder and Keying Options

The ML2051 NSA ships with a conventional 6-pin L4 keyway cylinder. IC prep versions are available: CL6 for 6-pin Large Format Interchangeable Core (less core) and CL7 for 7-pin LFIC. A Less Cylinder (LC) version is available for facilities sourcing their own cylinders separately. Available keying configurations include master keying, construction master keying, visual key control, concealed key control, 7-pin conventional, security cylinder, Access 3 cylinder, Pyramid high-security cylinder, and interchangeable core in small and large format. The ML2051 also accepts cylinders from most other manufacturers. For compatible cylinder options, browse cylinders, cores, and keys.

Available Finishes

605 Bright Brass, 606 Satin Brass, 612 Satin Bronze, 613 Dark Bronze, 619 Satin Nickel, 625 Bright Chrome, 626 Satin Chrome, 629 Bright Stainless Steel, 630 Satin Stainless Steel, 633 Aged Bronze, 643 Matte Black, 689 Aluminum, 690 Dark Aluminum, 693 Black, 695 Satin Nickel Plated Steel.