In Order Time a Sales Order cannot be Closed if it has a Kit with line items that haven't been cleared.
In the default Matrix view all of the Kit components can be seen, but in order to clear them we need to perform a few actions.
Start off by clicking the cog in the items tab to manipulate this List.
Click on the Columns Tab and Add the Cleared Column. Then click Save as seen below.
Then click on the Other Tab and change the View Type from Matrix View to Line View and hit Save:
Here we can see each Line Item in the Kit and we can tell they haven't been Cleared:
Click on each Line Item and click on the checkbox in the Cleared Column to Clear each one individually:
Once every Item has been Cleared you'll see check marks next to each one in the Cleared Column and the Status will automatically update to Closed:
You can always swap back to the Matrix View afterwards by clicking on the cog, going to the Other Tab, selecting it and hitting Save.