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diff --git a/en/SUMMARY.md b/en/SUMMARY.md
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+++ b/en/SUMMARY.md
@@ -20,6 +20,8 @@
     * [Survey](file_formats/survey.md)
     * [Rally Points](file_formats/rally.md)
     * [GeoFence](file_formats/fence.md)
+* [Developer Tools](tools/README.md)
+  * [Mock Link](tools/mock_link.md)
 * [Code Submission](contribute/README.md)
   * [Coding Style](contribute/coding_style.md)
   * [Unit Tests](contribute/unit_tests.md)
diff --git a/en/tools/README.md b/en/tools/README.md
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+# Developer Tools
+
+*QGroundControl* makes a number of tools available in debug builds. These ease common developer tasks including setting up simulated connections for testing, and accessing the System Shell over MAVLink.
+
+> **Note** [Build the source in debug mode](https://github.com/mavlink/qgroundcontrol#supported-builds) to enable these tools.
+
+Tools include:
+
+* [Mock Link](../tools/mock_link.md) - Creates and stops multiple simulated vehicle links.
+
diff --git a/en/tools/mock_link.md b/en/tools/mock_link.md
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+# Mock Link
+
+*Mock Link* allows you to create and stop links to multiple simulated (mock) vehicles in *QGroundControl* debug builds.
+
+The simulation does not support flight, but does allow easy testing of:
+
+* Mission upload/download
+* Viewing and changing parameters
+* Testing most setup pages
+* Multiple vehicle UIs
+
+It is particularly useful for unit testing error cases for mission upload/download.
+
+## Using Mock Link
+
+To use *Mock Link*:
+
+1. Create a debug build by [building the source](https://github.com/mavlink/qgroundcontrol#supported-builds).
+1. Access *Mock Link* by selecting the *Application Settings* icon in the top toolbar and then **Mock Link** in the sidebar:
+   
+   ![](../../assets/tools/mocklink_waiting_for_connection.jpg)
+   
+1. The buttons in the panel can be clicked to create a vehicle link of the associated type.
+
+   * Each time you click a button a new connection will be created.
+   * When there is more than one connection the multiple-vehicle UI will appear.
+   
+   ![](../../assets/tools/mocklink_connected.jpg)
+   
+1. Click the **Stop one Mock Link** to stop the currently active vehicle.
+
+Using *Mock Link* is then more or less the same as using any other vehicle, except that the simulation does not allow flight.