The part of this trade that nobody writes down.

Almost everything a building genuinely needs to know before it spends money on an entry system is unwritten. The statute exists, but it is statute: it tells you a Class A multiple dwelling of eight or more apartments erected after 1 January 1968 needs two-way voice and a remote door release, and it says nothing at all about what happens when the riser feeding that release has four usable conductors and the system you just approved needs six. The manufacturer documentation exists, but it is written to sell a product and it quietly assumes the wall is already open, the conduit is clear, and the panel is 90 feet from the head end rather than 340.

Everything between those two documents lives in the heads of people who are on a ladder at eight in the morning and are not writing anything down. So the knowledge only reaches a building at the worst possible moment. A super learns that the magnetic lock on that stair door was never legal when an inspector fails it. A board learns the riser has four conductors after it has voted through a video system that needs six, and after the reserve fund line has been published to shareholders. A restaurant owner learns where a camera cannot legally point when somebody complains, not when the camera was mounted.

These pages exist to move that information to the front of the process, where it is still cheap. They are written from jobs, from code text read directly rather than paraphrased from somebody else’s blog post, and from the arguments that actually happen in a basement with a flashlight and a tone generator.