This Attic Ceiling Ladder is Ceiling Mounted Type. It should be installed on the ceiling. Ceiling Opening Hole Size: 800mm x 900mm/31.5 x 35.4in. Thickness of the ceiling: 130-200mm/5.1-7.9in. The distance between opening hole and the wall should be greater than 50mm/2in. Please confirm these sizes before ordering. After installation 12 steps the maximum vertical height is 3m/9.8ft you can remove the steps to reduce the maximum height. Max. loading capacity: 660 lb. But this does not mean that this step ladder can stand on several people at a time. For your safety you should go up one by one. It is suitable for the attic roof top company warehouse hospital school etc. It is ideal for the installation and modification of the house.