My builder framed the joist opening, but wouldn’t install. Feared liability. I installed myself. Only comment is that I wish I instructions had been more clear about necessary clearance for Maschine mechanism. Enjoy 2 to 3 times the storage capacity and weight-bearing capability compared to competitors on the market today. https://attic-lift21975.pointblog.net/attic-lift-kit-dinge-zu-wissen-bevor-sie-kaufen-80424308