I finally looked up why old houses have those little doors on the roof, and I feel dumb
Spent 20 minutes on a ladder in Worcester last Tuesday arguing with a homeowner about a tiny hatch near her ridge, and she pulled up a 1911 building guide on her phone that called it a rooftop icebox door. I've been sweeping flues for 11 years and never once guessed it was for hauling ice up onto the roof to keep food cold in summer. What's the weirdest old fireplace feature you've had to explain to a customer?