# Ruler

The ruler can be used to measure lengths in the motion, optics and waves areas of the software. To show a measurement, the ruler must be connected to a hot spot on a part from one of these areas.

You cannot make measurements between parts in the motion, optics or waves areas because the scales are different. Parts have to be in the same area for the measurements to be valid.

Tips for use:

- The ruler can snap to hotspots.
- If large units are chosen to measure a small length, e.g. km chosen to measure a length of 50 cm, then 0 will be displayed for the length value. Change the units to something more appropriate to fix this.

## See also:

- Snapping to hot spots
- Marker
- Protractor
- Using presentation parts