While a sketch can contain segments and shapes, the contribution a sketch makes to its corresponding solid is limited to the covering produced by the sketch. For example, if an extrusion's sketch contains a rectangle, the profile used in the extrusion is that of the rectangle. That rectangle could be formed by using a rectangle shape element or four line segment elements in the sketch. If you use the rectangle, you witness the rectangular covering as you add the fourth segment. Intersections between all sketch elements are automatically performed as part of the covering process so you do not need to align the endpoints of the four segments. The following figure shows several ways to produce an identical covering and therefore an identical profile if used in an extrusion.
Holes can be generated in a sketch covering by using a connector. The following figure shows a hole produced by using two rectangle shape elements with a single line segment element connecting them.