What is this piece?

What is this piece at the right of the knob?

Is necessary for the normal assembling?

Thanks for your attention!

if it has 2x3 rows its for the AVR-Programmer connector.

Ah, I was wondering about that, too.

a|x

You don’t need it unless you want to upload new code to the MCU using an AVR ISP programmer.

Thanks boys! Great support!

Heh, that knob looks a little melty.