---
title: 'Join and slice tools'
linkTitle: 'Join and slice tools'
weight: 18
description: 'This section explains how to slice or join several labels'
---
In CVAT you can modify shapes by either joining multiple shapes into
a single label or slicing a single label into several shapes.
This document provides guidance on how to perform these operations effectively.
See:
- [Joining masks](#joining-masks)
- [Slicing polygons and masks](#slicing-polygons-and-masks)
## Joining masks
The **Join masks** tool (),
is specifically designed to work with mask annotations.
This tool is useful in scenarios where a single object
in an image is annotated with multiple shapes,
and there is a need to merge these shapes into a single one.
To join masks, do the following:
1. From the {{< ilink "/docs/manual/basics/CVAT-annotation-Interface/controls-sidebar#edit" "**Edit**" >}} block,
select **Join masks** .
2. Click on the canvas area, to select masks that you want to join.
3. (Optional) To remove the selection click the mask one more time.
4. Click again on **Join masks**
(**J**) to execute the join operation.
Upon completion, the selected masks will be joined into a single mask.
## Slicing polygons and masks
The **Slice mask/polygon** ()
is compatible with both mask and polygon annotations.
This tool is useful in scenarios where multiple objects in an image
are annotated with one shape,
and there is a need to slice this shape into multiple parts.
{{% alert title="Note" color="primary" %}}
The shape can be sliced only in two parts
at a time. Use the slice tool several times
to split a shape to as many parts as you need.
{{% /alert %}}
To slice mask or polygon, do the following:
1. From the {{< ilink "/docs/manual/basics/CVAT-annotation-Interface/controls-sidebar#edit" "**Edit**" >}} block,
select **Slice mask/polygon** .
2. Click on the shape you intend to slice.
A black contour will appear around the selected shape.
3. Set an initial point for slicing by clicking on the contour.
4. Draw a line across the shape to define the slicing path.
Hold Shift to add points automatically on cursor movement.
**Note**: The line cannot cross itself.
**Note**: The line cannot cross the contour more than twice.
5. (Optional)> Right-click to cancel the latest point.
6. Click on the contour (**Alt**+**J**) (outside the contour) to finalize the slicing.
