You will need your roof rack extension and bolt pack. Undo the x4 bolts from the rear runner of the extension. Keep the x4 M8x20 bolts you have just removed as we will be reusing these. Slightly undo the rest of the cross runners from the extension to allow for movement when fitting.

Remove rear runner and push extension into roof rack until the holes line up.

Take the x2 M8x55 bolts, spring and flat washers from your bolt pack and apply loctite. Fasten to roof rack like so yet keep loose for now. Repeat on other side.

Take the x4 M8x20 bolts that you removed from your extension before, apply loctite and screw in to the top of your roof rack. Still keep bolts loose for now. Repeat on other side.

Insert the cross runner you removed. Take the x4 M8x25 bolts from the bolt pack and apply loctite. Screw these into the cross runner. Repeat on other side.

Now that the roof rack is together, go around and securely fasten all bolts.

Depending on your vehicle, you may want to place your front cross runner upside down like so to prevent your roof rack from making too much noise while you drive.