The extrude face command is used to directly extrude the face(s) of individual mesh cells. This operation opens up the possibility of adding details to simple objects in a very flexible and intuitive manner. The Extrude Face tool button can be found in the Mesh Edit panel on the Mesh tab in the 3D Modeling workspace, as shown in the following screenshot:

The mesh cell face can be extruded directly using this command, as shown in the following step-by-step example:

1. Start the extrude face command, select the mesh face(s) to be extruded, and then press Enter.
2. Move the mouse cursor to specify the extrusion height. Alternatively, you can type the height value using the keyboard and then press Enter.
3. The extrusion is created and the command terminates:

Notice that in the previous example, if you move the mouse cursor downward (or entered a negative value for the extrusion height), a hole will be created in the mesh object, as shown in the following screenshot:

The extrude face command has two sets of options; the first set appears right after the command starts. This set has only one option, called Setting. To select this option, click on the option name in the command bar or, alternatively, type S and then press Enter. In the case of extruding multiple adjacent faces, this option controls whether the adjacent faces will be connected to produce a single extruded body, or whether each face will be extruded separately. The difference between these two settings may not be apparent in the case of mesh objects that are not sufficiently smooth. The following diagram shows the difference between the two settings using a smoothed mesh object:

The second set of options in the extrude face command appears after selecting the faces to be extruded. This set has three options, as shown in the following diagram:

The first option is called Direction. This option can be selected by clicking on the option name in the command line, or by typing D and then pressing Enter. By default, the extrusion will be created perpendicular to the mesh face. This option allows you to change the extrusion direction as desired by specifying two points representing the extrusion displacement vector. The following diagram shows an example of using the Direction option. The line end points are used to specify the direction vector:

The second option is called Path. To select it, click on the option name in the command bar or, alternatively, type P and then press Enter. This option allows you to set a custom path for the extrusion, as shown in the following diagram, where a polyline is used as an extrusion path:

The last option is called Taper angle. This option can be selected by clicking on the option name in the command line or, alternatively, by typing T then and pressing Enter. As the name suggests, this option adds a taper angle to the extrusion; a positive angle will taper the extrusion inward, while a negative angle will taper the extrusion outward, as shown in the following diagram:

Now that we have learned how to extrude the mesh faces, let's have a look at the next command, which is used to split them.