Polar
The Polar guide is similar to Ortho in that it aids in drawing on certain angles. Polar, however, is not limited to four angles. Also, while Ortho locks you into one of four angles, Polar snaps to designated angles, but also allows you to draw outside of the snapped angles.
To snap to an angle, move your cursor within 2-3 degrees if the angle. Once you are close the predefined angle, a dashed and dotted line will appear extending your line beyond your cursor. This indicates that Polar has snapped on to the angle.
Once you have snapped on to an angle, you can type a length into the command window and hit enter. The entity will follow the path of the angle specified by the mouse, and the length specified in the command window.
To change the designated angles, right click on the Polar button and select settings.
Here you can change the increments at which the Polar guide is displayed. You can also enter custom angles to which Polar will snap.