You can create a profile sketch, create a closed profile in the Line command, and close an open profile (close loop).
A profile is a single loop, multiple loops, intersecting loops, or islands. You can sketch on a planar face, and select one or more loops as the profile. All loops selected in a single operation are one profile.
A profile defines a cross section of a sketched feature . Use any closed 2D sketch (including model edges that join to form a closed loop ) as a profile for a feature. Extrude, Revolve, Sweep, Loft, and Coil features require profile sketches. When you create a feature, it consumes the profile.
Add dimensions or constraints to profiles to prevent them from changing size and shape. If you anticipate a change in the size or shape of a feature during the design process, underconstrain it. You can edit the sketch and add dimensions and constraints later.
For relatively close, but open sketch geometry, use Close Loop to create the closed profile that commands such as Extrude and Revolve require.
Coincident constraints perform the same function, but the Close Loop option avoids the tedious manual zooming and inspection of each intersection in a complex profile.
To remove a profile from the selection set, hold down Ctrl, and click the profile.
The program draws a final line segment to the starting point, and closes the profile. The Line command remains active.