Dwarvish Standard Door Pattern 87-D (Access Points, Securing, For The Use Of)

Pattern 87-D is a heavy door designed for defense against all grades of adversary.

Shown here with 2x Model 24 Periscope for surveilling both sides of the entrance, and a Type 2 Locking Portcullis, employed above a Western Type Granite 10-10 Corridor.

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Basic principles: A stone block 15’ high with footprint matching the corridor below is suspended above the corridor, anchored by locking pins operated by a quick-release lever (see attachment pp. 57-83). A single dwarf can easily release the block, which descends to completely block the passageway (and kill any intruders who happen to be underneath).

The block may be raised again by a winch mechanism, which can also be used to lower it slowly when speed is not required. Assuming a granite block 15′ × 10′ × 15′, an E-type quintuple reciprocated winch crewed by ten dwarves can typically raise the block at a rate of about one foot per ten minutes.

The passage under the block should slope outward with a gradient of 1 in 30 or steeper to prevent liquid-type attacks, and the approach should be slightly narrower than the block to deny attackers line-of-sight between the block and the wall. The block’s shaft should be lipped at the top to prevent attackers firing directly up into the guardhouse; this lip should be removable for maintenance.

Observation capability in front of the block is strongly recommended in order to avoid inadvertently raising it when an attacker is on the other side, and the gatehouse should be well defended (and preferably hard to access from inside the gate).

Due to the time required to operate this mechanism and the risk of damage, it should not be used as an everyday method of access control, only in emergency; for this reason, it should be augmented by other defences e.g. portcullis.

Operation:

The door may be deployed at the beginning of an attack to cut off all entry, but this may then prevent counter-attack, allowing enemies to fortify against the block and commence siege tactics. An effective strategy is to allow part of the enemy vanguard to pass before activating the block, isolating them while crushing the next in line, demoralising the enemy while reducing their numbers.

Modifications and Options:

  • Mechanical assist may be used to raise the block, however this increases vulnerability to infiltration by reducing the numbers needed to operate it. If such methods are employed, ensure an appropriate locking mechanism is used.
  • Repeated use may be highly damaging to the block and/or the floor below. A Type 7 friction-braking system may be employed to slow the block’s descent as desired, and in some cases reinforcing the floor may also be practical.
  • Tolerances should be considered carefully with regard to situational risk profiles. Some degree of gap between block and wall is necessary for maintenance, but may prevent an avenue of attack for missile fire, gas or flame weapons. Note that goblin-sized foes have been known to obtain ingress through gaps smaller than 6".
  • Lead sheeting is recommended as an anti-scrying feature and to prevent the passage of elemental-type threats.
  • Standard magical wards may be applied.
  • The use of automatic triggering mechanisms is NOT recommended. Due to the long opening time, antagonists might opt to trigger the release deliberately as a way of limiting defenders’ options.
  • If using in a higher-than-standard corridor, ensure the block is higher than the height of the corridor. Miscalculations on this issue can have very unfortunate consequences.

Dwarvish Standard Door Pattern 87-D (Access Points, Securing, For The Use Of)

Perfectly Legitimate Adventuring Party GeoffreyBrent