Deadbolts Explained: Single and Double Cylinder, Classroom, Thumbturn, Throw, Backset and Grades

When you replace a deadbolt or order one for a new door, start with what the key and the turn do on each side of the door. That is how the manufacturers' function tables below describe a deadbolt. The guide covers single cylinder, double cylinder, classroom, thumbturn and indicator deadbolts, mortise deadlocks, throw, backset and grades from those documents, and how our product names show them.

Single cylinder, double cylinder, classroom and thumbturn deadbolts

B500 Series functions, a selection from the function table in Schlage's B-Series service manual:

The B600, B700 and B800 Series use the same names, such as B660 single cylinder, B662 double cylinder and B663 classroom, plus the B664 cylinder lock (key on one side, no inside trim).

Kwikset's price book lists 660 and 980 as single cylinder (key outside, thumb turn inside), 665 and 985 as double cylinder, 663 as thumb turn only (no trim on the exterior) and 667 as thumb turn x plate (blank plate on the exterior). Arrow's and Medeco's catalogs also list cylinder x thumbturn (Arrow D61 and E61, Medeco function 0). Both catalogs use single cylinder for other versions too, such as Arrow's D63 and E63 (blank plate inside). Arrow calls D64 and E64 classroom: the turnpiece retracts the bolt but does not project it.

Double cylinder deadbolts

Schlage prints this caution with its B-Series function table: "Double cylinder locks on residences and any door in any structure which is used for egress are a life safety hazard in times of emergency and their use is not recommended. Installation should be in accordance with existing codes only." Medeco's catalog also lists a captive thumbturn, which converts the inside cylinder to a thumbturn while the facility or home is occupied.

Indicator and occupancy deadbolts

In the manufacturers' documents, an indicator shows whether the bolt is thrown. Schlage's B-Series manual marks the B571 Door Bolt Occupancy Indicator, which reads in use or vacant outside, as discontinued. The B572 door bolt has an inside turn unit and an emergency coin turn outside, with the indicator outside only, inside only or on both sides; see our Schlage B572-622 OS-OCC. The manual notes that the March 2024 indicator options are only compatible with a 2-1/8 inch bore. On Schlage's L496 mortise deadbolt, the message changes from blank to occupied when the bolt is thrown.

Mortise deadlocks: Schlage L400 and Sargent 8200

The B-Series deadbolts above fit a cross bore; the L Series manual lists Schlage's L400 functions as small case mortise deadbolts:

• L460: key outside, thumbturn inside
• L462: key both sides
• L463: key outside; the inside cylinder thumbturn retracts the bolt but cannot project it
• L464: key outside, no inside trim
• L480: thumbturn only, no outside trim
• L496: like the L460, with the indicator

Sargent's 8200/7800 mortise lock catalog lists deadbolt only functions under the caution "Deadbolt only functions not recommended for use on any door used for Life Safety egress": 8220 Deadlock (ANSI F18, key outside, no inside operation), 8221 Deadlock (F17, key outside, thumbturn inside), 8222 Deadlock (F16, key outside or inside) and 8203 Classroom Deadlock (F29, the thumbturn retracts the bolt but will not project it). Other 8200 functions combine a latchbolt and a deadbolt, such as 8225 Dormitory or Exit (F13); see our Sargent model numbers guide.

Deadbolt throw, backset and bore

• Throw. The documents give 1 inch for Schlage's B500, B600/700/800 and L Series deadbolts, Arrow's D and E Series, Sargent's 8200/7800 (1 inch projection) and Medeco's M3 Maxum.
• Backset. Schlage's B500 and B600/700/800 Series adjust for 2-3/8 or 2-3/4 inches; Arrow's D and E Series come in both, with a different standard front for each. The mortise locks list 2-3/4 inches: as standard in Schlage's L Series manual, and 2-3/4 inches only in Sargent's 8200/7800 catalog.
• Bore. Medeco's Maxum takes a standard 2-1/8 inch cross bore and 1 inch edge bore. Schlage's B571, B580, B581, B664 and B680 require a 1-1/2 inch cross bore.

Our door prep guide explains cross bore, edge bore and backset.

Deadbolt grades: read the grade for the series

• Schlage B500 Series: ANSI A156.36 (2010), Grade 2; B600/700/800 Series: A156.36-2010, Grade 1 auxiliary lock. With interchangeable core cylinders (see our SFIC vs LFIC guide), the same table prints Grade 2 (FSIC) or Grade 3 (SFIC).
• Schlage L400 mortise deadbolts: A156.36-2010, Grade 1.
• Arrow: A156.36-2020, Auxiliary Locks, Grade 1 for the D Series and Grade 2 for the E Series.
• Medeco Maxum: A156.36 Grade 1, printed for the Medeco 4 (M4) version.
• Sargent 8200 mortise locks: A156.13, Series 1000, Operational Grade 1 and Security Grade 1 with all standard trims.
• Kwikset: Grade 1 for the 980, 985 and 258 deadbolts; A156.40 Grade AAA for the deadbolt of the Halo Select.

BHMA titles A156.36 Auxiliary Locks, A156.13 Mortise Locks and A156.40 Residential Deadbolts; each standard has its own grades, so read a grade with its standard and series.

How our product names show type, finish and backset

Examples from our catalog, with what the number and name tell you:

• Schlage B663R626: B600 Series classroom deadbolt, finish 626
• Schlage L463P626RH: L463, finish 626, right hand
• Schlage L496P626: L496 indicator mortise deadbolt, finish 626
• Sargent 8203 26D: classroom deadlock, finish 26D
• Kwikset 663-15.DS: thumb turn only, named One-Sided Turn Deadbolt, finish 15 (satin nickel), 2-3/8 inch latch
• Medeco 11C604-T-26-DL-S: Maxum deadbolt, 2-3/4 inch backset
• Medeco 11-0A1922-24: Maxum bolt assembly

Medeco's catalog builds a Maxum number from 11 (Maxum deadbolt), the trim (C commercial, R residential), the cylinder type, the function and the bolt option, which sets the backset and front. So 11C604 is commercial trim, Medeco 6 pin cylinder, cylinder x thumbturn, 2-3/4 inch backset with a 1 inch front, followed by T (M3 technology), the finish 26, the keyway DL and S (sub-assembled, uncombinated). Bolts have their own numbers. The 2-3/4 inch Maxum bolt with a 1-1/8 x 2-1/4 inch faceplate is 110A1922 (our 11-0A1922-24), and the 1 x 2-1/4 inch version is 110A1921.

See also our Schlage model numbers guide (including B60 and B62 deadbolts), Kwikset guide, Arrow guide, finish codes chart (626, 622, 26D) and door handing chart (RH).

Deadbolts at The Builders Supply

• Residential deadbolts
• Commercial deadbolts and deadlocks
• Lock parts and components

Not sure which deadbolt function, backset or grade you need? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].