I am talking about the knob which screws into the end of the centre board to allow you to raise & lower it with your foot. This is from a 2007 Rio - I'll have to check if still the same deal on the current ones.

Managed to leave it behind when de-rigging over the summer - so if anyone has one to sell I'd be much obliged.

Before it gets suggested I'll point out that I have emailed the main Starboard dealer in France by the way...