Main toolbar > Fence Select Region (Selection Region flyout)
The Fence Selection Region button, available from the Selection Region flyout, provides one of three methods you can use to select objects by region. The other two methods are Rectangle and Circular.
For all three methods, you can select either objects that are completely within the selection region (window method), or objects that are either within or touched by the selection shape (crossing method). Toggle between the window and crossing selection methods by using the Window/Crossing button on the status bar.
Procedure
To select using a fence:
Click the Fence Selection Region button.
Drag to draw the first segment of a polygon, then release the mouse button.
A "rubber-band line" is now attached to the cursor, anchored at the point of release.
Move the mouse and click to define the next segment of the fence. You can make as many steps as you want.
To complete the fence, either click the first point, or double-click.
A crosshair appears when you're near enough to click the first point. This creates a closed fence.
Double-clicking creates an open fence, which can select objects only by the crossing method.
To cancel the selection, right-click before you release the mouse.