In isometric, it is possible to work directly with measurements only on the main axes. Here you can learn what you have to do if you need a measure beyond the main axes.

A direct use of the ruler is only possible on the main isometric axes and only if you do not work with perspective reductions.
 
The measurements between the axes are drawn with different reduction factors. If you wish to determine a measurement on an object that is not parallel to the axes, you can easily do this by using an ellipse. The graphic below shows an object that is not parallel to the axes:


 
Now, if you wish to add a bevel, for example, you have to ablate the measurement from the upper edge. In order to do this without the outer line lying on the main axis, you should use one or more ellipses that are given the appropriate diameter (2 x the measurement). Then, connect these ellipses with a line (marked blue in this example). Now, you have the outer line in the right distance from the bevel:


 
Thus, you can also create the lower edge and work out the bevel:


 
The helper ellipse therefore equals a perspective pair of compasses.