From FreeCAD Documentation
- Optionally select one or more base objects, for example Draft Lines and Draft Wires:
- Draft Wires with two or more segments will be used to create landings. They must be on a plane parallel to the global XY plane. For example, select a U-shaped wire for a half-turn landing and an L-shaped wire for a corner landing.
- Draft Lines will be used to create flights.
- If the vertices of all lines and wires have correct Z coordinates, the created stairs will use this information.
- The base objects must be selected in the correct order starting with the bottom object.
- Press the Arch Stairs button, or press S, R keys.
- Adjust the desired properties. Some parts of the stairs, such as the structure, might not appear immediately, if any of the properties makes it impossible, such as a structure thickness of 0.