Holding Shift or Ctrl While Creating Polygons

• Hold Shift to create an irregular polygon whose shape is determined by the position of the mouse pointer.
• Hold Ctrl (command in Macintosh) to create a regular polygon with a horizontal base.

  Drag while holding Shift.

  Drag while holding Ctrl (command in Macintosh).

  The Ctrl and Shift keys can be used at the same time.