Fill Gaps in Sketch add-in scans a sketch and attempts to detect and fill gaps between endpoints of lines and curves in the sketch. It is particularly useful in an imported woodworking sketch geometry.

Steps:

1. Press the "Fill Gaps" button in the "Sketch" panel.
2. Enter a gap width. Fill Gaps will attempt to fill gaps smaller than the specified gap width.
3. Select the fill or join mode.
   The fill attempts to add a new line between endpoints and attempts to keep the geometry unchanged.
   The join attempts to join two curves. It changes the geometry and a whole shape of curves.
4. Check the delete double checkbox to delete double lines. Double arcs and splines aren't supported in the current version.
5. Check the project geometry checkbox to project the geometry to a new sketch. It flattens the geometry, but calculates longer.
6. Press "OK" button.

Please check if all curves exist and have the right whole shape after filling the gaps, especially in the join or project modes.

Help online: https://maciejrogowski.com/fill-gaps-help/

Install:

1. Download the installer from Autodesk App Store.

2. Right-click on the "Downloads" folder and select "Open in Finder".

3. Right-click on the "FillGaps.bundle-macos.pkg" -> "Open With" -> "Installer". 

Uninstall:

You can unload the add-in without uninstalling it by clicking the "Stop" button when the add-in is selected in the list box on the "Add-Ins" tab of the "Scripts and Add-Ins" dialog.

Unchecking "Run on Startup" causes the add-in not to be loaded in future sessions of Autodesk® Fusion 360™.

- Navigate to ./ApplicationsPlugins folder and select the app bundle you want to uninstall

- Either drag the app bundle to the Trash, or right-click and select “Move to Trash”

- Right-click on the Trash-Can and select “Empty Trash”

- If you prefer keystrokes, you can also just select the app bundle and then hit Command+Delete to move the app to Trash, then empty the Trash and the app will be removed.