SOLIDWORKS gives users the ability to create sketches using multiple contours. These contours go on to further define regions that can also be selected for feature use. Below is an example of a multiple contour sketch.

First some terminology:

Contours – Sketch entities (lines, arc,…) that form a closed region.
Regions – the area enclosed by a contour.

In the case of creating a simple Boss Extrude, selecting a specific contour prompts SOLIDWORKS to extrude the entire area encompassed by the contour. The examples below show the results of selecting the outermost contour and on the right from selecting only inner contours.

In situations where various contours are needed, they can be added individually to the selected contours box of the feature property manager.

By utilizing multiple contours within sketches, SOLIDWORKS users are capable of creating the entire part without the need for multiple features.