Why do Arduino boards have that Tab at their rear?

Hi,
Can someone explain why Arduino boards are not fully rectangular? They all have a tab about 35mm long at the rear of their boards.

Best Regards,
Jim

Massimo answered this already:

http://forum.arduino.cc//index.php?topic=2022.msg17829#msg17829

"Remember that Arduino started as a tool for designers.... and plain green rectangles are sooo boring.... only an engineer would find a green rectangle exciting

so we decided to give it a special shape... david quartielles came up with the shape and I picked the colour "

Italians, masters of design - that's why we chose to keep that 50 mil spacing on the header, to give you grief :smiley:

// Per.