Loiding: Latch Bypass, the Word's Origin, and Deadlatch Defenses

Origin of the Word

"Loid" is short for celluloid, the early plastic. Green's Dictionary of Slang records the noun as an abbreviation of celluloid meaning a strip of celluloid or plastic used to slip open "Yale-style locks when housebreaking," with its earliest citation in Lilliput in 1949. A 1959 citation in the same dictionary notes the nickname "Celluloid Jack" for a man said to be the first to use strips of celluloid that way. Dictionary.com dates the word to 1955–60 and defines the verb as opening a locked door "by sliding a thin piece of celluloid or plastic between the door edge and doorframe to force open a spring lock." The slang record is older than that dictionary dating; both agree the word comes from celluloid.

What Is Being Defeated

A spring latch is not a deadbolt. The Lock Industry Standards and Training (LIST) Council's Professional Locksmith Dictionary defines a latch bolt as "a spring actuated bolt, normally with one or more beveled surfaces, which, when aligned with the strike, engages it automatically." A spring latch, in the same dictionary, is "a latch operated under spring pressure, having no deadlatching feature." Because the bolt is spring-loaded and beveled, end pressure from the door gap can, in principle, push it back. That is the design weakness loiding exploits. A deadbolt, by the LIST definition, "requires a deliberate action to extend, and which resists end pressure in the unlocking direction when fully extended." End pressure alone is not enough against a properly extended deadbolt.

Deadlatching as the Design Answer

Hardware makers answered the spring-latch problem with deadlatching. The LIST dictionary defines a deadlocking feature as one that, "when fully engaged, resists attempts to move the latch or bolt in the unlocking direction through direct pressure," and a deadlocking latch as "a latchbolt with a deadlocking mechanism."

Trade writing treats that feature as a security baseline. Locksmith Ledger's guidance on electric strikes states that if a latch can be shimmed, "either the lock does not have a deadlocking feature, or the deadlocking pin is not being held in the proper position," and that "locks that don't have some version of deadlatch pins are really not designed for security applications." The same article advises choosing an electric strike whose faceplate "maintains the deadlatch functionality," and mentions pry guards and anti-jimmy plates that cover the latch area. Allegion's Schlage lock-function descriptions specify, for functions such as the storeroom lock, that an "auxiliary latch deadlocks latchbolt when door is closed."

Installation still matters. A deadlatch that does not engage because the strike is wrong, the door gap is large, or the latch is misaligned is no better than a plain spring latch. See bypass for the broader point that the assembly, not only the cylinder, sets the security of an opening.

Covertness and Detection

Loiding is often discussed as a low-damage method. The LIST dictionary defines surreptitious entry as techniques "that cannot be detected via disassembly and detailed inspection," and covert entry as techniques that can be detected only by such inspection. Whether a given opening leaves marks depends on the hardware and the attempt. Locksmiths and investigators look at latch faces, strike edges, and door-gap conditions when they evaluate a scene. See forensic locksmithing.

Ethics and Law

Authorized use for a lockout, with the owner's permission, is a legitimate locksmith service. Unauthorized use is burglary. TOOOL Netherlands states that its most important rule is "to only open locks that you have permission for to open from the owner." California Penal Code § 466 lists possession of "picklocks, ... or other instruments or tools" with intent to break or enter as a misdemeanor. Laws vary by place. This article gives no legal advice. See lockpicking for more documented examples.

Related Topics

• Bypass
• Deadbolts
• Latch
• Electric strikes
• Lockpicking
• Forensic locksmithing

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