Marks USA 21AC Entrance Double...
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$299.00
$99.81
Marks USA 21AC Entrance Double Cylinder Unilock Mortise Lock with Round Knob, 605 Bright Brass finish, mortise body and trim shown

Marks USA 21AC Entrance Double Cylinder Unilock Ornamental Iron Mortise Lock with Round Knob

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Model: 21AC/3-W-RHR
$299.00
$99.81
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In Stock (leaves warehouse same day if ordered before 3pm ET)

$299.00
$99.81
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Marks USA 21AC Entrance Double Cylinder Unilock Ornamental Iron Mortise Lock with Round Knob

The Marks USA 21AC is a commercial-grade entrance mortise lock built for storm doors and ornamental iron door applications. It fits 1" door thickness, uses a Series 9 lock body with a 2-1/2" backset, and delivers a 1" bolt throw with 1/2" latch projection. The lock front measures 1" x 7-1/8". Trim assemblies are thru-bolted solid brass, and spring-loaded captivated spindles provide consistent operation. ANSI/BHMA certified and UL Listed.

Key Features

  • Door Thickness: Fits 1" door thickness, suited for ornamental iron and storm door applications.
  • Series 9 Lock Body: 2-1/2" backset for accurate fitment across compatible door preparations.
  • Bolt and Latch: 1" bolt throw and 1/2" latch projection; reversible for flexible handing.
  • Lock Front: 1" x 7-1/8" for a clean fit within the door mortise pocket.
  • Thru-Bolted Solid Brass Trim: Eliminates threaded swivel spindles for superior long-term security.
  • Uni-Lock Single Screw Assembly: Single screw assembly simplifies installation and reduces installation time.
  • Spring-Loaded Captivated Spindles: Steel hub construction with helper springs for smooth, consistent operation over the life of the lock.
  • Double Cylinder: Keyed operation on both sides for entrance security on ornamental iron and storm doors.
  • Lifetime Mechanical Warranty: Backed by Marks USA's Lifetime Mechanical Warranty.

Certifications and Compliance

  • ANSI/BHMA Certified
  • UL Listed
  • Commercial Grade
  • Lifetime Mechanical Warranty

Technical Specifications

  • Door Thickness Range: 1"
  • Backset: 2-1/2"
  • Bolt Projection: 1"
  • Latch Projection: 1/2"
  • Lock Front: 1" x 7-1/8"
  • Hub Material: Steel
  • Trim Material: Solid Brass (thru-bolted)
  • ANSI/BHMA: ANSI/BHMA, UL Listed
  • Commercial/Residential: Commercial
  • Product Type: Mortise Lock
  • Series: 21 Series

Typical Applications

  • Ornamental iron storm door entrances
  • Commercial office building entry points
  • Educational facility exterior doors
  • Retail establishment entrance doors
  • Multi-tenant residential property common entrances
  • Government and municipal building access points
  • Industrial facility entrance and security doors

About the Marks USA 21 Series

Marks USA has been a primary manufacturer of ornamental iron storm door locks for decades, developing the Uni-Lock single screw assembly, thru-bolted solid brass trim, and spring-loaded captivated spindles with steel hubs. The 21AC carries ANSI/BHMA certification and UL listing for commercial entrance applications where security and installation efficiency are both required.

Manufacturer Resources

Marks USA Product Catalog

Product Specs

Series:
21 Series
Features:
1/2" Latch Projection; Spring Loaded Captivated Spindles
Product Group:
Mechanical Locks
Product Subgroup:
Mortise Locks
Product Type:
Mortise Locks
Subcategory:
Mortise Locks
ANSI/BHMA:
ANSI/BHMA, UL Listed
Commercial/Residential:
Commercial
Front Size:
1" x 7-1/8"
Hub Material:
Steel
Product Attribute:
Mortise Locks
Electronic:
No
Door Thickness Range:
1"
Product Category:
Mechanical Locks
Backset (Distance):
2-1/2"
Department:
Door Hardware

Marks USA 21AC/3-W-RHR – Frequently Asked Questions

1) Will the Marks USA 21AC mortise lock fit a 1 inch thick ornamental iron storm door?
That is exactly the door it is built for. The 21AC is a single-thickness lock sized for 1 inch doors, which is the thin stile you get on ornamental iron and storm doors. It is not a lock for a standard 1-3/4 inch commercial door. If your opening is a conventional hollow metal or wood door, look at a full-size mortise lockset like the Cal-Royal NM8050 instead, which is set up for 1-3/4 inch doors.
2) What backset and lock front size do I need to prep the door for a Marks 21AC?
Prep to a 2-1/2 inch backset with a 1 x 7-1/8 inch front. The body is a Series 9. Those three numbers are what decide whether it drops into an existing iron door pocket, so measure the old front and the hole center before ordering; a 2-3/8 or 2-3/4 inch backset prep will not line up.
3) Will the 21AC latch into the strike that is already on my iron door frame?
The 21AC throws a 1 inch bolt and has a 1/2 inch latch projection. A 1/2 inch latch needs a strike lip and pocket deep enough to take it, and the 1 inch deadbolt needs a full bolt hole in the jamb. If the door currently carries another Marks 21 Series storm door lock with the same 2-1/2 inch backset and 1 x 7-1/8 inch front, the existing strike normally carries over. Coming off a different maker's lock, plan on a new strike.
4) Do I have to order the Marks 21AC by hand, or is it reversible?
The lock body itself is reversible, but it is ordered as a handed item: left hand reverse or right hand reverse. Both of those are outswing doors, which is what an ornamental iron storm door almost always is. Stand outside, look at the hinges. Hinges on your left and the door swings toward you is LHR; hinges on the right swinging toward you is RHR.
5) What do I have to specify when ordering the Marks 21AC besides the finish?
Three things: handing (LHR or RHR), finish (626 satin chrome or 605 bright brass), and keying. Keying is a required choice of keyed different, keyed alike, or none if you are supplying your own core. On a building where every tenant gets their own key, take KD. For a property manager who wants one key to open every gate and storm door on the site, take KA.
6) Is the Marks 21AC double cylinder, and does that mean a key on the inside too?
Yes, key both sides. Double cylinder means no thumbturn inside, so anyone leaving has to key out. That is why it gets used on iron storm entrances next to glass, but it is a problem on any door in a required means of egress, and a lot of jurisdictions will not pass it. If you need free egress from inside, a single cylinder function is the right call.
7) What is the closest alternative to the Marks USA 21AC for a standard 1-3/4 inch commercial door?
The Marks USA 21AC is built for 1 inch door thickness, which is the thin stile of an ornamental iron or storm door, not a standard commercial door leaf. For a 1-3/4 inch door with a 2-1/2 inch backset mortise body, the Baldwin 6310 is an entrance/storeroom mortise lock body with a 2-1/2 inch backset that covers 1-3/8 inch and over, and the Baldwin 6301 entry/apartment body shares the same 2-1/2 inch backset for doors 1-3/4 inch and over. Both keep the backset dimension the 21AC uses while fitting the thicker leaf.
8) If I need a keyed mortise lock but want a lever instead of a knob, what should I order?
The Marks USA 21AC comes with a round knob. For a keyed mortise lockset on a lever, the Baldwin 6301LS is an entry/apartment lever by lever body on a 2-1/2 inch backset for doors 1-3/4 inch and over, and the Baldwin 6310190RRLS is a right hand reverse lever by lever entry/storeroom mortise lock on the same 2-1/2 inch backset. The Accentra 8805FL is a Grade 1 storeroom mortise lock with an Arcadia lever in the 8800 Series. All three carry the lever trim the 21AC does not.
9) Is the Alarm Lock DL2700CR a weatherproof substitute for the Marks USA 21AC on an exterior storm door?
They do not fit the same door. The Marks USA 21AC is sized for 1 inch door thickness. The Alarm Lock DL2700CR Trilogy T2 is a weatherproof electronic mortise lock with a classroom function and a Grade 1 rating, but its door thickness range is 1-5/8 inch to 1-7/8 inch, so it will not prep into a 1 inch ornamental iron stile. It is also keypad operated, where the 21AC is a mechanical, non-electronic lock keyed on both sides.
10) Can a Schlage PC10 replace the Marks USA 21AC?
No. The Schlage PC10 is a Grade 1 cylindrical lock, non-keyed passage with a rose, for 1-3/4 inch doors - it bores through the door face rather than seating in a mortise pocket. The Marks USA 21AC is a mortise lock with a 1 inch by 7-1/8 inch lock front that drops into a mortise cut, on a 2-1/2 inch backset for 1 inch doors, and it is keyed on both sides. The two preps are not interchangeable. Where a mortise pocket is already cut, the Schlage PM010 Grade 1 passage latch mortise lock is the mortise equivalent of the PC10.
11) The Emtek 3102 Memphis looks like a mortise entrance lockset - will it work where a Marks USA 21AC is specified?
No. The Emtek 3102 Memphis mortise entrance lockset is a dummy function, as are the Emtek 3104 Hamilton and 3106 Manhattan - dummy trim does not latch, lock, or accept a key. The Marks USA 21AC is a commercial entrance double cylinder lock with a working 1 inch bolt, a 2-1/2 inch backset and a Marks A keyway cylinder on both faces. Use an Emtek dummy only on an inactive leaf where no latching is wanted.
12) Is a Hager 3800 Series mortise lock a drop-in for the Marks USA 21AC?
No, the preps differ in two ways. The Marks USA 21AC uses a 2-1/2 inch backset and fits 1 inch doors. The Hager 3810S and 3810E are Grade 1 passage mortise locks on a 2-3/4 inch backset for doors 1-3/4 inch to 2-1/2 inch, and the Hager 3850E office function shares that 2-3/4 inch backset and thickness range. Different backset and a much thicker leaf means the mortise pocket and cross bore will not line up with a 21AC prep.
13) What keyway and cylinder does the Marks 21AC use, and can I master key it?
It ships with the Marks "A" keyway, 5-pin, two keys, and comes keyed alike in sixes, so a set of doors opens on one key out of the box. That leaves it master keyable within a Marks A system. If your building is standardized on a different keyway, order the keying option as none and fit your own core.
14) How is the knob trim mounted on the Marks 21AC, and will it loosen up on a high-traffic gate?
The trim is solid brass and thru-bolted rather than hung on a threaded swivel spindle, which is the part that backs off and goes loose on cheap storm door locks. Spindles are captivated and spring loaded, running on steel hubs. On a multi-tenant entrance gate cycled all day, that thru-bolt and steel hub combination is the reason to pick it over a residential storm door lock.
15) Does the Marks 21AC carry any certification for a commercial spec job?
It is ANSI/BHMA certified and UL Listed, and it is a commercial rated lock rather than a residential one. That covers the usual submittal line on an ornamental iron entrance. It is entirely mechanical, no power, no wiring, so there is nothing to coordinate with an access control contractor.
16) I want keypad or card access on my iron entrance gate. Can I use the 21AC?
No. The 21AC is a mechanical key-only lock with no electronic option. For credentialed access on a mortise prep, the Alarm Lock DL2700CR Trilogy T2 is a weatherproof keypad mortise lock, though it is built for 1-5/8 to 1-7/8 inch doors, so it will not go on a 1 inch iron door. On a thin-stile aluminum or iron opening with an Adams Rite style deadlatch, the Alarm Lock DL1300NW Trilogy Networx is the keypad lock made for that prep.
17) What else uses a 2-1/2 inch backset mortise body if the 21AC is not the right function?
The Baldwin 6301 knob by knob and 6301LS lever by lever are entry/apartment mortise bodies on the same 2-1/2 inch backset, and the Baldwin 6310 is the entry/storeroom version. Watch the door though: the 6301 bodies are listed for 1-3/4 inch and over and the 6310 for 1-3/8 inch and over, so on a 1 inch iron storm door the 21AC is the one that fits.
18) I just need a deadbolt on the iron door, not a knob lockset. What should I look at?
If there is no latching function needed, a straight mortise deadbolt is simpler. The Sargent 4874 is a double cylinder mortise deadbolt on a 2-3/4 inch backset, and the Kaba Ilco 185 Series is a no-handing mortise deadbolt. The 21AC differs in that it combines a knob-operated 1/2 inch latch with a 1 inch bolt in one body, so the door latches shut on its own instead of relying on someone throwing a bolt.
19) Can I match the 21AC across a run of storm doors on one property?
Yes, and that is the usual buy. It is offered in 626 satin chrome and 605 bright brass, in left hand reverse and right hand reverse, so a mixed run of outswing gates can all take the same lock and the same knob look. Order keyed alike and one key runs the lot. Match the finish to the existing trim and the only thing that changes door to door is the handing.
20) What is the difference between the Marks USA 21AC and the Sargent 4874 mortise deadbolt?
Both are double cylinder devices, but they do different jobs. The Marks USA 21AC is a double cylinder entrance mortise lock with a round knob, a 1 inch bolt and a 1/2 inch latch projection, so it latches the door on closing and locks with a key from either side. The Sargent 4874 is a double cylinder mortise deadbolt on a 2-3/4 inch backset with no latch and no knob trim, so it secures a door that is held closed by something else. If the opening needs both the latching function and the knob, the 4874 is not a replacement for the 21AC.
21) What is a Grade 1 keyed mortise lockset to standardize on across a facility instead of the Marks USA 21AC?
The Marks USA 21AC is a commercial ANSI/BHMA and UL Listed mortise lock for 1 inch doors. For standard 1-3/4 inch facility doors where a facility wants one Grade 1 platform, the Cal-Royal NM8050 is a heavy duty Grade 1 office/entrance mortise lockset with an auxiliary deadlatch, the NM8080 is the Grade 1 storeroom version with an interchangeable core option, and the NM8070 is the Grade 1 classroom version. All three are listed at 1-3/4 inch door thickness, so they suit the standard leaf rather than the ornamental iron stile the 21AC serves.
22) I do not need the door keyed from both sides - what is a simpler mortise lock than the Marks USA 21AC?
The Marks USA 21AC is a double cylinder entrance lock, keyed on both sides. Where an opening only needs latching with no key, the Schlage PM010 is a Grade 1 non-keyed passage latch mortise lock for 1-3/4 inch doors, and the Falcon MA101 is a Grade 1 heavy duty mortise passage lock with field reversible operation and a fire rating. For a keyed exterior with a thumbturn on the inside instead of a second cylinder, the Cal-Royal NM8050 is a Grade 1 office/entrance mortise lockset. Note that these peers are built for 1-3/4 inch doors, not the 1 inch stile the 21AC fits.
23) What should I use instead of the Marks USA 21AC if the entry needs credential or keypad access?
The 21AC is a mechanical, non-electronic lock with a Marks A keyway cylinder on each side. For credential-based entry on a mortise prep, the Dormakaba E-Plex E5086 is a Grade 1 entry/egress electronic pushbutton and card mortise lock in a back to back configuration, the Accentra NTM623-NR is a Grade 1 nexTouch Generation 3 mortise lock with a capacitive touchscreen keypad and cylinder override, and the Schlage LEMD-GRW is a Grade 1 ENGAGE Series wireless mortise lock with a 125kHz proximity reader and a 3 hour fire rating. These are electronic platforms rather than a keyed swap for the 21AC.
24) Is the Kaba Ilco 185 Series mortise lock the same kind of part as the Marks USA 21AC?
They are both mortise devices for narrow openings but they are not equivalents. The Kaba Ilco 185 Series is a deadbolt function mortise lock supplied with no handing. The Marks USA 21AC is an entrance double cylinder latching lock with a 1 inch bolt and a 1/2 inch latch projection, and it is handed at the order stage in left hand reverse or right hand reverse, though the body itself is reversible. If the storefront or iron door needs the knob and the latch, the 185 does not provide either.
25) Which mortise lock should I use for a classroom or dormitory door rather than the Marks USA 21AC?
The 21AC is an entrance double cylinder function, which keys the door from both sides and is not the classroom or dormitory security function. For a classroom door, the Corbin Russwin ML2003 is a Grade 1 mortise classroom lockset for 1-3/4 inch doors in the ML2000 Series, and the Cal-Royal NM8070 is a heavy duty Grade 1 classroom mortise lockset with an auxiliary deadlatch. For a dormitory corridor door, the Sargent 7925 is a Grade 1 heavy duty dormitory exit function mortise lock with rose trim and a single cylinder deadbolt.
26) What is the difference between the Marks USA 21AC and the BEST 45HCAC mortise lock body?
The Marks USA 21AC ships as a complete lock with thru-bolted solid brass trim assemblies, round knobs and double cylinders, on a 2-1/2 inch backset for 1 inch doors. The BEST 45HCAC is a heavy duty mortise lock body with a public entrance function and field reversible operation - a body, so trim and cylinder are specified separately. The BEST 45HCAINL is the same heavy duty body line with an intruder function. Both BEST bodies suit a standard commercial leaf rather than the ornamental iron stile the 21AC is dimensioned for.
27) What mortise lock handles a bathroom or bedroom door where the Marks USA 21AC would be the wrong function?
The Marks USA 21AC is keyed on both sides, which is not appropriate for a bath or bedroom door. The Cal-Royal NM8440 is a heavy duty Grade 1 privacy mortise lockset with a deadbolt for 1-3/4 inch doors, and the Hager 3840S is a Grade 1 privacy mortise lock on a 2-3/4 inch backset for doors 1-3/4 inch to 2 inch. Both give the occupant-side privacy function rather than the two-sided key control of the 21AC.
28) How hard is the Marks 21AC to install on an existing iron door?
Trim goes on with the Uni-Lock single screw assembly, so the knob and rose come together as one thru-bolted unit rather than a stack of loose parts and a threaded spindle you have to cut to length. Assuming your pocket already takes a 1 x 7-1/8 inch front at a 2-1/2 inch backset, it is a drop-in on a 1 inch door.
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Does the Marks USA 21AC/3-W-RHR come with a warranty?
Absolutely. The Marks USA 21AC/3-W-RHR is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
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