About Extruding Mesh Elements
You can extrude faces and border edges on the control mesh to add new faces to the control mesh. The new faces are created by duplicating the selected face and connecting the duplicated face and the original face with parallel edges. The extrude length is the length of the shortest edge of the selected mesh elements. You can select multiple faces or edges for extrusion. If you have selected both edges and faces for extrusion, the first selection type is retained. That is, if you have first selected the faces and then the edges, all the edges are discarded. Any vertices in the selection are automatically ignored.
You can extrude mesh elements in a linear direction using the handles of the dragger. The direction of the movement of the handle decides the direction of the extrusion.