Kwikset 665 Double Cylinder Deadbolt: Security Through Both Sides

The Kwikset 665 operates by a key on both the exterior and interior — that’s the defining characteristic that sets this deadbolt apart from standard residential locks. Ideal for doors with glass panels or windows within 3 feet, it addresses a specific security vulnerability that thumb-turn deadbolts can’t handle.

Double Cylinder Design and Installation Specs

The 665 prevents an intruder from breaking glass and reaching in to unlock the door. That’s real security logic for Montana ranch homes with decorative glass sidelites or properties where door windows sit within arm’s reach of the deadbolt.

The installation requirements match standard residential door prep:

Specification	Measurement
Cross bore	2-1/8 inches
Edge bore	1 inch
Backset	Adjustable to 2-3/8 inches or 2-3/4 inches
Door thickness	1-3/8 inches to 1-3/4 inches standard
Throwbolt	Full 1-inch solid-core

Fits standard door preparations without modification. Fully reversible to fit both right-handed and left-handed doors.

SmartKey Technology vs Pin-Tumbler Systems

SmartKey Security allows re-keying the lock in seconds with any KW1 keyway key — no locksmith, no disassembly. BumpGuard patented side-locking bar technology replaces traditional pin-and-tumbler design to protect against lock bumping.

Stainless steel side-locking bar, racks, and pins for increased strength and security separate this from basic pin-tumbler mechanisms. The SmartKey version offers easier re-keying and better bump protection than the standard pin-and-tumbler 665.

Simple 3-step process using the SmartKey tool makes re-keying practical for property managers or homeowners who change tenants regularly.

Security Grade Reality Check

The 665 is an ANSI/BHMA Grade 3 (Residential/Medium Security) lock. That’s honest residential-grade security, not commercial-grade pretense. Higher models like the 785 or 994 series are Grade 2 (Commercial/High Security).

Approximately 4.3 to 4.4 out of 5 stars across customer reviews shows solid real-world performance. The largest-selling deadbolt in America, the 600 series provides tough, effective protection at an affordable price.

Who Should Use Double Cylinder Deadbolts

Requires a key for exit from the interior; should be used with caution in emergency exit routes. Double cylinder locks do not meet ADA requirements for ease of operation without two hands/key.

The 665 makes sense for:

• Exterior doors with glass panels or nearby windows
• Detached shops and garages where emergency egress isn’t primary
• Secondary entrances not used as fire exits
• Rural properties where break-and-reach attacks are a concern

Skip it for main home entrances where family members need quick emergency exit.

What’s in the Box

The 665 kit includes everything needed for installation:

• Exterior and Interior Deadbolt Assemblies
• Adjustable Latch
• 2 Keys
• Strike Plate (both round-corner and full-lip options)
• Mounting Hardware
• SmartKey Re-key Tool
• Installation Instructions

Coverage is typically valid for the original purchaser while they occupy the home under Kwikset’s lifetime mechanical and finish warranties.

FAQ

Can I re-key the Kwikset 665 to match my existing house keys? Works with any Kwikset KW1 key. The SmartKey system lets you re-key to match any KW1 keyway key in seconds using the included tool.

Will the 665 fit my old door that currently has a different brand deadbolt? Requires 2-1/8 inch cross bore and 1 inch edge bore — standard measurements that match most existing residential deadbolt preparations.

What’s the actual security difference between the 665 and higher-grade Kwikset deadbolts? The 665 is an ANSI/BHMA Grade 3 (Residential/Medium Security) lock. Higher models like the 785 or 994 series are Grade 2 (Commercial/High Security). Grade 2 locks undergo more rigorous cycle testing and force resistance requirements.

Can I install different finishes on the inside and outside? The 665 comes as a matched set. Both sides feature the same finish — in this case, satin nickel.

Is the backset truly adjustable or do I need to order a specific size? Adjustable to 2-3/8 inches or 2-3/4 inches (Note: some specific SKUs may be fixed at 2-3/8 inches) — check the specific model number to confirm adjustability.