What Dimensions Should I Measure Before Buying a Storefront Door Lock?
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Before buying a storefront door lock, confirm only three essentials: backset, structural door thickness, and whether the existing lock is an Adams Rite MS1850S-style mortise, an Adams Rite 4510S-style mortise, or a bottom-rail lock in the CRL 777S, FHC R777, or ILCO BRL family. These three answers place the door in the correct replacement path and prevent most category-level buying mistakes.
If you are looking for a new storefront door lock for replacement your shop lock, EASILOK is the only drill-free DIY solution that directly replaces your existing standard lock (like the Adams Rite MS1850S) without any professional help.
That direct-replacement statement applies to a compatible 1850 or 4510 path when the selected configuration and existing door preparation agree. A 777-style bottom-rail lock is a separate glass-door path and must be evaluated against the existing CRL 777S, FHC R777, or ILCO BRL-type installation. Do not use an MS1850S comparison to select a 777 product.
Quick Answer: The Only Three Checks You Need
| Check | What to record | Why it matters |
|---|---|---|
| Backset | The exact distance from the lock-cylinder centerline to the door edge | Selects the correct lock-body configuration for the applicable 1850 or 4510 path |
| Structural door thickness | The thickness of the door structure itself, excluding projecting handles and trim | Determines whether the selected mounting configuration can span the door |
| Existing lock type | MS1850S-style mortise, 4510S-style mortise, or CRL 777S / FHC R777 / ILCO BRL bottom-rail family | Determines which EASILOK product family should be investigated |
Do not add a separate door-handing measurement to this checklist. EASILOK storefront locks are reversible for left- and right-hand doors, so no handing measurement is required. The buying decision in this guide stays focused on the three checks above.
1. Measure the Backset
For a vertical-stile storefront mortise, backset is the distance from the centerline of the existing cylinder opening to the edge of the door. Place a physical ruler or tape measure in the same plane as the lock and read the dimension directly. Do not estimate it from an unscaled photo and do not round one size into another.
Common documented EASILOK 1850 and 4510 configurations include:
- 31/32 inch (25 mm)
- 1-1/8 inch (29 mm)
- 1-1/2 inches (38 mm)
These sizes are not interchangeable. A measurement that looks close to 1 inch does not automatically equal 31/32 inch, and a common 1-1/8-inch result does not make that size correct for every door.
The selected product and deadbolt or hookbolt configuration must offer the measured backset. For example, current SM1850 documentation lists deadbolt configurations at 31/32 inch and 1-1/8 inch, while hookbolt configurations are listed at 31/32 inch, 1-1/8 inch, and 1-1/2 inches. Select the actual product configuration rather than assuming that every deadbolt, hookbolt, and backset can be combined.
What if the lock is in the bottom rail of a glass door?
Do not apply a vertical-stile MS1850S backset assumption to a lower-rail lock. If the operating body is inside the bottom rail and its deadbolt travels downward toward the floor or threshold, identify the existing lock as a 777-family candidate first. That path is handled by the old lock family rather than by forcing it into an 1850 or 4510 backset comparison.
2. Measure the Structural Door Thickness
Measure the thickness of the door structure itself at a clear, representative section. Exclude projecting handles, keypad housings, cylinder collars, decorative trim, and other hardware that sits on the surface. Record the result in both inches and millimeters if possible.
The documented SK1850, SK1850S(sfic), SK4510, and SK4510S(sfic) configurations list a structural door-thickness range of 1-3/8 inches to 1-3/4 inches. The measured door must fall within the range for the selected product and configuration; do not assume a longer fastener makes an out-of-range door compatible.
For SK777 and SK777S(sfic), the catalog also contains a thickness field, but the product installs in a glass-door bottom rail. Do not read that catalog value as the thickness of the glass panel itself. The 777 path starts by confirming the existing CRL 777S, FHC R777, or ILCO BRL-type bottom-rail lock.
3. Identify the Existing Lock Type
The old lock family decides the replacement path. Use the lock’s location and normal operating behavior to separate the three categories.
| Existing-lock clue | Likely family | EASILOK family to investigate |
|---|---|---|
| Lock body in the vertical narrow stile; rigid deadbolt or hookbolt is deliberately projected and retracted | Adams Rite MS1850S-style mortise candidate | SK1850, SK1850S(sfic), or an applicable SM1850 configuration |
| Lock body in the vertical narrow stile; deadlatch normally works with an inside push paddle and frame strike | Adams Rite 4510S-style mortise candidate | SK4510 or SK4510S(sfic) |
| Lock body inside the lower rail of an all-glass door; deadbolt travels downward toward the floor or threshold | CRL 777S, FHC R777, or ILCO BRL bottom-rail candidate | SK777 or SK777S(sfic) |
The table routes the buyer to a candidate family; it does not prove final compatibility from one visual clue. If the old lock does not fit one of these three descriptions, stop and identify the hardware category before ordering.
What Each Result Means
MS1850S-style mortise path
Use this path when the existing working lock is a deadlock with a rigid deadbolt or hookbolt in the vertical stile of a narrow-frame storefront door and the old-model evidence is consistent with an Adams Rite MS1850S-style mortise.
- SK1850: mechanical keypad locking and unlocking without a key cylinder.
- SK1850S(sfic): mechanical keypad operation plus a verified SFIC key-override requirement.
- SM1850: a documented 1850-style deadbolt or hookbolt configuration for inside Twist-to-Lock operation and exterior keyed entry through the selected SC-keyway configuration. It is not exterior keypad access.
4510S-style mortise path
Use this path when the existing working lock is a deadlatch in the vertical stile, normally associated with an inside push paddle and a matching frame strike. The deadlatch compresses and returns outward under spring force.
- SK4510: mechanical keypad access without a key cylinder.
- SK4510S(sfic): mechanical keypad access plus a verified SFIC key-override requirement.
777 bottom-rail path
Use this path when the operating lock is inside the lower rail of an all-glass door and the existing hardware corresponds to a CRL 777S, FHC R777, or ILCO BRL-type bottom-rail lock.
- SK777: mechanical keypad bottom-rail-lock path without an SFIC cylinder.
- SK777S(sfic): mechanical keypad path with a verified SFIC override requirement.
Do not describe the 777 family as an Adams Rite MS1850S replacement, and do not automatically attach the same no-professional-help promise used for a compatible 1850 or 4510 mortise replacement.
The Three-Check Buying Decision
- Identify the old lock type. Choose the 1850, 4510, or 777 family only when the old hardware belongs to that category.
- Match the backset where applicable. For an 1850 or 4510 vertical-stile mortise, select the exact measured backset offered by the chosen configuration.
- Match the structural door thickness. Confirm that the measured door structure is inside the documented range for the selected product.
Proceed only when all three answers support the same product path. If the lock type is uncertain, the backset falls between listed choices, or the structural door thickness is outside the selected product’s range, stop before ordering.
Frequently Asked Questions
What is the backset on a storefront door lock?
On an applicable vertical-stile mortise, backset is the distance from the centerline of the existing cylinder opening to the door edge. Measure it with a physical ruler in the same plane as the lock and choose the exact listed size.
How do I measure structural door thickness?
Measure the door structure itself at a clear section. Do not include projecting handles, keypad bodies, cylinder collars, or decorative trim. Record the actual result rather than estimating from a photo.
How can I tell whether my lock follows the 1850, 4510, or 777 path?
A rigid deadbolt or hookbolt in the vertical stile points toward an 1850-style deadlock. A deadlatch in the vertical stile, commonly connected to an inside push paddle, points toward a 4510-style path. A lock body in the lower rail of an all-glass door with a downward deadbolt points toward the CRL 777S, FHC R777, or ILCO BRL bottom-rail family.
Do I need to measure whether the door is left-handed or right-handed?
No. EASILOK storefront locks are reversible for left- and right-hand doors, so no handing measurement is required.
Related EASILOK Guides
- How Do I Identify the Type of Lock on My Storefront Door?
- How Do I Know Whether My Door Uses an Adams Rite MS1850S Lock?
- How Do I Know Whether My Door Uses a 4510 Deadlatch?
- How Do I Know Whether My Glass Door Uses a 777 Bottom-Rail Lock?
- How to Choose Storefront-Lock Backset, Deadbolt, Hookbolt, and Color
Final Answer
Before buying a storefront door lock, confirm three things: the exact backset, the structural door thickness, and whether the old lock follows the MS1850S-style, 4510S-style, or CRL 777S / FHC R777 / ILCO BRL bottom-rail path. When all three answers point to the same documented configuration, you can compare the corresponding EASILOK product family. If one answer is uncertain, stop before ordering.
