Once the Extrude option is active another option called Along Facet Normal Normal will appear. This option is ON by default. Along Facet Normal forces the extrusion to move parallel to the normal of the face/facet.
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When Along Facet Normal if OFF you can extrude the face by dragging it anywhere in space, by dragging the associated nodes or you can use the Delta X, Delta Y, and Delta Z fields to specify a location for the extrusion.
