> For the complete documentation index, see [llms.txt](https://docs.imerit.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.imerit.net/labeling/labeling-tools/tools/polyline.md).
# Polyline
Overview of the Polyline labeling tool in Ango Hub
The polyline labeling tool allows you to draw a line on an image.
{% hint style="info" %}
The Polyline tool is supported across the Image, Video, DICOM, and Medical labeling editors.
{% endhint %}
## The Polyline Labeling Tool in Ango Hub
### How to add a Polyline tool to your project
From the project’s *Settings* tab, enter the *Label Set* section.
Click on *Add Category*. From the list that appears, click on *Polyline*.
A new row will appear named *Polyline*. Click on it to expand it.
Give your polyline tool a title and description.
Enable the *Required* toggle if you want to force labelers to create a polyline on every asset. When the toggle is disabled, labelers will be able to save and move to the next asset without creating a polyline label using this class.
If you would like to ask labelers further questions, for example, if you want to show a further *radio* after drawing the polyline, click on *Add Classification* and add a further question. More[ on nested questions here](/labeling/labeling-tools/tools/nested-classifications.md).
### How to Draw a Polyline
Click on the image where you’d like the first point of the polyline to be. Click again where you’d like the second point to be, and so on. When you are done, press *N* on your keyboard to finish the polyline.
While drawing, you may click anywhere with the right mouse button to delete the last point you have placed.
To edit a polyline's points, select it by clicking on it, then drag the polyline itself or one of its points.
On images and videos, right-click a point on a selected polyline to remove it. A polyline must keep at least two points.
### Measuring pixel distances
On images and videos, a polyline with exactly two points shows the distance between them in pixels. Place the two points, press *N* to finish the polyline, then hover over or select it to see the length in the object details overlay.
In the editor settings, enable *Show Object Details on Hover* and leave *Hide Object Dimensions* unchecked to see the measurement. The length updates as you drag either endpoint.
Polylines with three or more points do not show a length. On DICOM images, use the existing line measurement tool instead.
### Snapping to an angle
On images and videos, hold *Alt* (⌥ on macOS) while drawing a polyline segment or dragging one of its points to snap the segment to 15-degree increments, such as 0°, 15°, 30°, or 45°.
## Edge Sharing
While drawing a polyline, if you press E, Hub will highlight the points of other polygons, polylines, and points. By clicking on the other object's points, you can snap your current polyline's points to them:
By snapping at least two points to the existing polygon and holding Alt (⌥ on macOS) + clicking, you can quickly anchor a series of points to the existing object, as shown in the GIF above.
---
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