You can restrict cursor movement to the current horizontal and vertical axes so that you can draw at right angles, or orthogonally. For example, with the default 0 degree Orientation (angle 0 at the "three o'clock" or "east" position), when the Draw Orthogonal option is enabled, lines are restricted to 0 degrees, 90 degrees, 180 degrees, or 270 degrees. As you draw lines, the rubber banding line follows either the horizontal or vertical axis, depending on which axis is farthest from the cursor. When you enable the isometric snap and grid, cursor movement is restricted to orthogonal equivalents within the current isometric plane.
Ortho mode and polar tracking cannot be on at the same time. Turning on Ortho turns off polar tracking.
To enable orthogonal drawing
Status bar click
SETTINGS: Specifies settings for Snap mode, grid, and polar and object snap tracking
SNAP: Restricts cursor movement to specified intervals
System Variables Reference
OSMODE: Sets running Object Snap modes
OSNAPCOORD: Controls whether coordinates entered on the command line override running object snaps
POLARANG: Sets the polar angle increme
POLARDIST: Sets the snap increment when the SNAPSTYL system variable is set to 1 (polar snap)
POLARMODE: Controls settings for polar and object snap tracking
SNAPTYPE: Sets the snap style for the current viewport