From Nevercenter 3D Modeling Wiki
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Menu Path: Create > Extrusion Object
The Extrusion Object command will extrude a surface along an axis to create a 3-dimensional shape.
- The amount of extrusion.
- The extrusion will be divided into this many sections.
- The axis along which the extrusion is performed.
- Extrusion Object will work on a 3-dimensional shape such as a cube, but usually should be used on relatively flat non-closed shapes such as a polygons, line segments or grids.
- Extruding an object that consists of faces will create a closed object (caps on the end), whereas extruding an object that consists of only edges (e.g. a line segment) will create an object that is open on the ends.