When activated, this tool will select features on the map by left-click multiple times to draw a polygon. A right click will close the polygon, and all features within the polygon will be selected.
To activate this selection mode, choose the Select by Drawing Polygon button from the Selection toolbar, or choose POLY SELECT - Draw Polygon to Select Features found under the Advanced Selection Options sub-menu of the Digitizer menu or context menu.
When this selection mode is turned on, the toolbar button will remain highlighted. Choose this option again to toggle it off and return to the normal selection mode of clicking or clicking and dragging to draw a box.