There are two types of extrude in SolidWorks, Boss-extrude and Cut-Extrude. The main difference between these two is that Boss-extrude is used to add material, and Cut-Extrude is to remove material (read more about add and remove material here).
Accessing the Function
The easiest way to access these two functions is through the icon on the ribbon.
Alternatively, these functions could be accessed by clicking Insert > Boss/Base > Extrude for Boss-Extrude or Insert > Cut > Extrude for Cut-Extrude.
Extrusion Options
Opening up the menu, there are few features that you can play with.
Starting Condition
The starting condition defines where the extrusion would start. By default, it would be from the sketching plane. However, you could select other options such as from specified surface, or by defining an offset distance from the sketch plane.
Starting Condition Options
End Condition
The end condition options allow you to determine how you are going to terminate the extrusion feature. The default is on blind, where you specify the depth of the extrusion. You could use a surface to specify the depth of the extrusion in the event where the desired depth is not known.
End Condition Options
Draft Angle
The draft-angle option allow you to create a draft angle along the extrusion instead of having it perpendicular to the sketching plane. For example, applying draft angle on a circular sketch would result in a conical shape as shown below.
Draft Angle Option
Thin-Feature
The thin-feature function allow you to create a hollow solid with certain wall thickness.
Thin-feature option
You can have cap-ends function as well to have the center section to be end-capped. The thickness of the cap is user defined.
Effect of having end-caps option
Selecting Contours
In the event where there are more than one closed-loop region in the sketch, you could select which region you want to extrude using the selected-contours option. For illustration, there are four closed loop region shown in figure below, and two are selected to be extruded.
Selected Contours option
This operation would result a solid which looks like this:
Resulted Solid
