By Kent · Lock Depot Staff Writer

The letter after 9K37 is the whole job

A Best 9K37 part number reads like a code, and the letters right after the 37 decide what the lock does. Order a 9K37T and a 9K37W for the same hallway and one lets a resident in with a push of a button while the other makes everyone, inside and out, use a key. Both are the same Grade 1 cylindrical chassis. Both fit the same prep. Only the function changes, and the function is what you are buying. This guide walks through four of the less common letters: T dormitory, C corridor, W institutional and IN intruder. We also point out the two everyday ones, R classroom and D storeroom, so you can see where these four sit.

What stays the same on every 9K37

The listings describe the 9K series as listed by the BHMA to A156.2, Series 4000, Grade 1, and ideal for retrofit and new construction. Every one we are covering has a 2-3/4 inch backset, is non handed, fits 1-3/4 to 2-1/4 inch doors only, and has a solid brass 9/16 inch latch throw with a deadlocking latchbolt. The lever is the style 14, curved with a return, on a 3 inch convex rose, and all mounting screws are concealed. The housing is 7-pin and accepts all Best cores. The core is not included, so you order it separately and match it to your keying. Our guide on rekeying a Best core without a locksmith visit shows why that matters. If you are choosing between the 9K and the 45H for a school, read the 45H versus 9K comparison first.

9K37T: dormitory

The 9K37T14CSTK626 is the dormitory function. The listing describes it as a single cylinder lock. The latch is operated by rotating the inside lever, and by rotating the outside lever when it is not locked by key or push button. The outside lever is locked by turning the key in the outside lever or by pushing the button on the inside lever. The inside lever cannot be locked.

That last point is the reason this function exists for a bedroom door. A resident can push the button and lock the outside from the inside. A key from the corridor side can lock or release it too. Whoever is inside can always walk out without a key. It is a lock for rooms where the occupant controls the door on a normal day and the building has a key as the override.

9K37C: corridor

The 9K37C14CSTK626 is the corridor function. This one is listed as a double cylinder function, with a key cylinder on both sides. The latch is operated by rotating the inside lever, and by rotating the outside lever when it is not locked by key. The outside lever is locked by turning the key in the inside lever. The inside lever cannot be locked.

Note what is missing: there is no push button. Staff lock the outside from the inside with a key, and anyone inside can still leave at any time. This is the pattern for an interior door off a corridor where the lock is controlled by staff, not by the person in the room. It is a different job from the dormitory function even though the two read alike on a punch list.

9K37W: institutional

The 9K37W14CSTK626 is the institutional function, and it is the strictest of the set. The listing says the latch is operated by turning the key in the inside lever and turning the key in the outside lever, and that both levers are always fixed. In plain terms, neither lever works without a key. There is no free egress by lever.

That is a serious restriction. Use it only where a code-compliant opening is not required to let a person out freely, such as a secured area in an institution where staff control every entry and exit. If the door is anyone's means of egress, the W function is the wrong choice. Confirm the use with your authority having jurisdiction before you order it, and do not install it on an exit route to save money on a different lock.

9K37IN: intruder

The 9K37IN14CS3626 is the intruder function. It is a double cylinder lock where the latch is operated by rotating the inside lever, and by rotating the outside lever only when it is not locked by an inside or outside key. The outside lever is locked by turning the key in the inside lever, and the inside lever cannot be locked. Free egress stays intact.

The listing adds two details the others do not have. The intruder function includes an interior indicator rose as standard, so someone inside can see at a glance whether the outside is locked. And its strike differs: the SKU ends in CS3, and the listing gives a strike that conforms to ANSI A115.2 for 1-3/4 inch doors, measuring 4-7/8 by 1-1/4 inches with a curved lip. The other three ship with the standard STK strike, 2-3/4 by 1-1/8 inches. Check your frame prep before you order. A frame cut for the short strike does not take the long one without work.

Where R and D fit

Two common functions give you a reference point. The 9K37R classroom lock is a single cylinder: the outside lever is locked and unlocked by turning the key in the outside lever, and the inside lever cannot be locked. The 9K37D storeroom lock is a single cylinder where the outside lever is always fixed and can never be unlocked without the key, while the inside lever is always free. Our earlier piece on 9K30 privacy versus 9K37 entrance shows the 37 family at the other end of the range.

Side by side

• T dormitory: single cylinder, inside button or outside key locks the outside, inside never locked.
• C corridor: double cylinder, inside key locks the outside, no button, inside never locked.
• W institutional: double cylinder, key needed on both sides, both levers always fixed.
• IN intruder: double cylinder, inside key locks the outside, indicator rose, long ANSI strike.

Common ordering mistakes

The first is swapping T for C because both look like a hallway lock. T gives the occupant a button. C gives only staff a key, so a resident cannot lock the door from the inside without one. The second is ordering W for a door people must exit freely. The third is forgetting the core: every listing says the core is not included, so the lock arrives with an empty housing. Fourth, ignoring the strike on the IN. See the full lineup on the Best lock page.

Common questions

What is the difference between the Best 9K37T and 9K37C?

The T is a single cylinder dormitory lock with an inside push button. The C is a double cylinder corridor lock with no button, where the outside is locked by turning a key in the inside lever.

Does the Best 9K37W allow free exit?

No. The listing says both levers are always fixed and need a key to operate. Do not use it where the door is a required means of egress.

Does the Best 9K37IN come with a core?

No. The listing says the core is not included. It has a 7-pin housing that accepts all Best cores.

What strike comes with the Best 9K37IN?

The listing gives a strike that conforms to ANSI A115.2 for 1-3/4 inch doors, 4-7/8 by 1-1/4 inches with a curved lip. The T, C and W ship with the standard STK strike.

What door thickness do these locks fit?

The listings say 1-3/4 to 2-1/4 inch doors only, with a 2-3/4 inch backset.