Deadlatch

a deadlatch is a high-security locking device that allows two-way traffic for applications requiring free entrance at certain times and exit-only at other times. it provides a higher level of security than a standard spring latch through the use of a deadlock plunger. when the door closes, this secondary plunger is held back by the strike plate, which deadlocks the main latch. this mechanism is specifically engineered to prevent "shimming" or "loiding"—a common break-in method using a credit card or similar tool. once deadlocked, the latch can only be retracted by turning a key or the interior handle. common areas of use;

• retail storefronts: enabling free entrance for customers during business hours and secure, exit-only traffic after closing.
• commercial offices: securing aluminum stile doors to prevent unauthorized bypass techniques while maintaining easy egress for employees.
• industrial facilities: managing two-way traffic in secure environments that require robust protection against forced entry.
• apartment buildings: protecting shared residential entryways from common loiding attacks while ensuring residents can safely exit.
• how a deadlatch works: the key feature of a deadlatch is the deadlock plunger (a smaller, secondary bolt located next to the main latch bolt).
• when the door is open, both the main latch and the plunger extend.
• when the door is closed, the main latch enters the strike plate hole, but the plunger is held back by the face of the strike plate.
• as a result, when the plunger is depressed while the main latch is extended, the main latch becomes "deadlocked." it cannot be pushed back in manually, meaning it can only be retracted by turning the key or the interior handle.