Use this menu option to toggle the display of the rulers in the 2D and 3D views.
You can use the rulers adjacent to the X axis and Y axis of the 2D and 3D views to make measurements.
In the 2D view, the ruler along the X axis also displays the
units of measurement (millimeters or inches) used in the current model.
You can change the colour of the rulers in the 3D view in the
Drawing Options area of the Options panel.
See also