Best Mortise Deadbolts - 48H Series

The BEST 48H Series is the auxiliary mortise deadbolt line from BEST Access Systems, now part of the dormakaba family of brands. If you searched "best 48h", "mortise deadbolt", "mortise deadbolts", "best mortise lock catalog", "best mortise deadbolt", "best mortise lock brand", or "best mortice locks" — every product in this category is stocked and ships same day from American Locksets. 

What Makes BEST One of the Best Mortise Lock Brands in Commercial Hardware

BEST Access Systems has been specifying commercial mortise hardware for institutional facilities for decades. Schools, hospitals, universities, government buildings, and high-security commercial environments consistently specify BEST because of one core advantage: the BEST interchangeable core system. BEST's SFIC (Small Format Interchangeable Core) and LFIC (Large Format Interchangeable Core) platforms allow facilities to rekey every door in a building in minutes without disassembling hardware or calling a locksmith. Insert a control key, remove the old core, drop in a new one — the door is rekeyed. For a university with thousands of openings or a hospital that changes staff constantly, that rekeying speed is a genuine operational advantage over conventional cylinder systems.

Every 48H Series mortise deadbolt in this category accepts all BEST cores through its 7-pin SFIC housing. The 7-pin format provides more key differs than a 6-pin system — more unique key combinations available for large master key hierarchies — and accepts the full range of BEST standard, high security, and restricted keyway cores.

The BEST 48H is now sold under the dormakaba brand following the acquisition of Stanley Security's commercial hardware division, which included BEST. The product numbers, specifications, and core compatibility all carry forward directly.

What a Mortise Deadbolt Is and Why It Differs from a Mortise Lockset

Mortise Deadbolt vs Mortise Lockset: The Critical Difference

This is the most important distinction to understand when specifying the 48H Series. The BEST 48H is a deadbolt-only mortise device. It has no latchbolt, no levers, and no automatic door retention. The 48H throws a deadbolt and that is its sole function.

The BEST 45H, by contrast, is a full mortise lockset — it includes a latchbolt, levers, and a deadbolt all in one body. The 45H handles the primary locking function on a door. The 48H does not. The 48H is an auxiliary deadbolt, installed as a secondary lock on a door that already has a primary latchset, adding a dedicated keyed deadbolt above or below the primary hardware without adding a second full mortise lockset to the door.

In commercial construction, auxiliary mortise deadbolts appear on stairwell re-entry doors, corridor access points, apartment and hotel room entry doors, office suites, and any opening where an additional deadbolt layer is specified in addition to the primary lock. Specifiers who write "48H" into a hardware schedule are calling for a supplementary deadbolt on top of whatever primary lock is already there.

BEST 48H Series Functions: K, L, M, and R

The 48H Series ships in four primary function configurations. Each is designated by a letter suffix in the model number.

K — Single Cylinder, Key Outside and Thumbturn Inside The K function is the standard single cylinder deadbolt. Key retracts and extends the deadbolt from outside. A thumbturn retracts and extends the deadbolt from inside. The inside occupant can lock and unlock the bolt without a key. Correct for office suites, apartment entries, and hotel rooms where inside control is needed. The BEST 48H-7-K-626 is this configuration in satin chrome.

L — Cylinder Outside Only, No Inside Trim The L function provides a key-operated cylinder outside and no inside trim. The deadbolt is operated by key from outside only. Used for closet locks, service room access, or any opening where inside control is not required. The deadbolt cannot be extended or retracted from inside without a key.

M — Double Cylinder, Key Both Sides The M function requires a key from both sides to operate the deadbolt. No thumbturn inside. Life safety codes restrict double cylinder deadbolts on required egress paths — confirm with the authority having jurisdiction before specifying M function on any door in the egress system. Correct for high-security applications where key control from both sides is required and egress codes permit it.

R — Classroom, Cylinder Outside with Inside Thumbturn The R function is the classroom configuration. Key from outside locks and unlocks the outside cylinder function, but the inside thumbturn always operates the deadbolt freely. The BEST 48H-7-R-626 is the classroom variant in satin chrome.

The 7-Pin SFIC Housing and Concealed Internal Set Screw

Every 48H in this category ships with a 7-pin SFIC housing less core. The core is ordered separately. BEST SFIC cores — combinated, uncombinated, or grand master keyed — drop directly into the housing without any tool other than the control key.

The mortise cylinder in the 48H housing has a concealed internal set screw that secures the cylinder to the lock case. The set screw is accessible only after removing the SFIC core with a control key. This prevents the cylinder from being unscrewed and removed by an attacker without a key — a security detail absent from many competing mortise deadbolt designs and rarely mentioned on any competing product page.

Specifications, Door Prep, and Thick Door Availability

The 48H case is 0.095-inch cold rolled steel, 3-3/8 inches by 4-3/16 inches by 1 inch, zinc dichromate plated for corrosion protection. Deadbolt is stainless steel, 1-inch throw. Backset is 2-3/4 inches. Door thickness is 1-3/4 inches standard. Thick door configurations are available up to 3 inches — specify thickness when ordering. Note: the R (classroom) function is not available in the thick door configuration.

Standard strike is 48HS1 flat, 3-1/2 inches by 1-1/8 inches by 3/32 inches, fitting ANSI A115.5 door frame prep. Lipped strike 48HS2 is 4-7/8 inches by 1-1/4 inches by 3/32 inches for ANSI A115.1 prep. Faceplate is brass or bronze, 5-3/8 inches by 1-3/16 inches by 7/32 inches.

UL listed for 3-hour A label fire doors. ANSI/BHMA A156.13 Series 1000 Grade 1. Finishes available in all finishes offered for the 45H Series — 605, 606, 612, 613, 619, 626, 626AM, 629, 630, 643e and others.

Frequently Asked Questions: BEST 48H Series Mortise Deadbolts

Q: What is the BEST 48H Series? 

The 48H is BEST's auxiliary mortise deadbolt — deadbolt only, no latch or lever. Installed as a secondary deadbolt alongside a primary mortise lockset. Now a dormakaba product.

Q: Is BEST a good mortise lock brand?

 Yes. BEST has been the institutional standard for commercial mortise hardware for decades, specified in schools, hospitals, universities, and government buildings nationwide. Now part of dormakaba.

Q: What is the difference between BEST 48H and 45H? 

The 45H is a full mortise lockset with latch, levers, and deadbolt. The 48H is an auxiliary deadbolt only — no latch, no lever. The 48H is a secondary lock installed alongside the primary lock.

Q: What do the function codes K, L, M, R mean on the 48H?

• K — single cylinder, key outside, thumbturn inside

• L — cylinder outside only, no inside trim

• M — double cylinder, key both sides

• R — classroom, key locks/unlocks outside, thumbturn inside always works

Q: Can double cylinder (M function) be used on egress doors? 

Generally no. Life safety codes prohibit double cylinder deadbolts on required egress paths in most jurisdictions. Confirm with the authority having jurisdiction before specifying.

Q: What is the deadbolt throw on the BEST 48H?

 1-inch stainless steel throw. Case is 0.095-inch cold rolled steel, zinc dichromate plated. Backset is 2-3/4 inches standard.