Doors, Frames, and Gaps
Door assemblies form the primary physical perimeter of buildings and secured interior suites. The relationship between the door leaf, frame, and threshold dictates which non-destructive bypass vectors are physically viable.
Deadlatch Alignment & Latch Slipping
Figure 1: Proper auxiliary deadlatch pin depression (deadlocked against shove knife) vs misaligned strike installation permitting bypass. Source & Reference: BHMA Door Hardware Guidelines & Deviant Ollam Door Bypasses.
The deadlocking auxiliary pin is a critical defense on latch mechanisms:
- When installed properly, the main latch bolt falls into the strike opening while the smaller auxiliary pin remains depressed against the flat strike plate face, mechanically deadlocking the main bolt.
- If the strike plate is misaligned or oversized, the auxiliary pin falls into the strike opening, leaving the spring latch completely vulnerable to slipping with a shove knife or credit card.
Door Swing Directions
| Swing Type | Identification | Primary Bypass Vectors |
|---|---|---|
| Outswing (Pulls Toward Exterior) | Exposed hinge barrels on exterior face | Latch slipping (shove knife), Under-Door Tool (UDT), hinge pin removal |
| Inswing (Pushes Toward Interior) | Latch bevel faces outward, hinges internal | Latch slipping, Credit card/mica slip, thumbturn manipulation |
| Double Doors | Two meeting door leaves with central meeting stile | Crash bar bypass through meeting stile, astragal manipulation |
Gap Analysis & Tolerances
- Undercut (Bottom Gap): The space between the bottom of the door leaf and the finished floor or threshold. Standard gaps of 3/8" to 3/4" allow deployment of the Under-Door Tool.
- Latch Reveal (Meeting Gap): The gap between the door edge and the strike jamb. Excessive gaps expose the deadlatch or main latch bolt, allowing direct manipulation.
- Top & Transom Gaps: Spaces above doors or adjacent glass panes that allow reaching egress sensors or handles with specialized wire tools.
Vulnerabilities & Applicable Bypasses
Defensive Countermeasures
- Installing full-height latch protector plates (astragals) on outswing doors.
- Installing commercial-grade brush or neoprene door sweeps to eliminate undercuts.
- Ensuring deadlocking auxiliary pins are properly seated in the strike plate without extending into the cutout.