> ## Documentation Index
> Fetch the complete documentation index at: https://docs.spine.altician.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Ruler Tool

> Display distances between points on the 3D volume

## Activation

Click the **Ruler** button in the toolbar to activate measurement mode.

## Usage

1. Click on the volume to place the **first point**.
2. Click again to place the **second point**.
3. The distance between the two points is displayed in **millimeters (mm)**.

## Notes

* Distances are calculated in world coordinates using the DICOM spatial reference.
* Multiple measurements can be taken.

<Note>
  Distances are approximate and not validated for clinical measurement.
</Note>

<Warning>
  Activating the Ruler tool automatically deactivates **Pointer** and **W/L**. Only one interaction tool can be active at a time.
</Warning>