I saw a post earlier with a set of hinged stairs. These were the stairs in my old house in St. Louis, Missouri. Installed in the 1940s by a company called the St. Louis Stair Co. They’re counterweighted so no prop is necessary to hold them open. They were installed so that people living in upstairs apartments could access the basement without going outside. We actually met the daughter of the man who owned the company and patented these stairs, she helped install ours.