Sublime
An inspiration engine for ideas
The main door of the hall is a dense medieval affair, shot through with bolts: siege-proof. On either side sit two stone lions, lichen mottling their manes. It seems wrong to use such an entrance, but there is no other way, no tradesman’s signpost. She pushes the bell and a ferrous donging sounds within.
Sarah Hall • The Wolf Border
Always consider the relative strengths and weaknesses of doors, windows, walls, floors, ceilings, etc. All should be equally strong from a defensive standpoint: attackers will target the “weakest link in the chain” and should not find a weak spot to expose. Examples of “weakest link” design include a concrete wall with a hollow-core door, or a gyps
... See moreEric Conrad, Seth Misenar, Joshua Feldman • CISSP Study Guide

But its green wooden door opens not to reveal a rag rug and a woodstove but yet another door—a serious-looking door made of thick steel that can be breached only with the right combination of keys, codes, and security cards. Behind it are cameras and a motion detector.
Elizabeth Royte • Bottlemania: Big Business, Local Springs, and the Battle over America's Drinking Water
[We send you now into the maw of a forgotten castle of the black dragons, locked in time by the working of a Monarch with skills beyond mortal comprehension. If the two of you can siphon but the fraction of power within, you will soar to the skies…but only if you do not crumble before their mighty will.]
Will Wight • Dreadgod (Cradle Book 11)
A shadow flowed from beneath the only door in the room, unfolding into a hunched figure wearing a dark gray cloak. The fabric was worn and tattered with age, and breath hissed from the darkness in his hood. “I think we opened the wrong door,” Renfei said.
Will Wight • Cradle, Path of Gold: Box Set (Cradle Collection Book 2)
Furthermore, soldiers used none of the streets, roads, alleys, or courtyards that constitute the syntax of the city, and none of the external doors, internal stairwells, and windows that constitute the order of buildings, but rather moved horizontally... See more
Geoff Manaugh • Nakatomi Space

This means lights over entrances, locking the doors, and reinforcing windows.