pls. clarify
I had submitted a signature card when I had filed for I-485 last Aug. I'm not sure if the rules changed after that but I guess it would be better if we get more responses to clarify.
A signature card is nothing but a piece of paper (couldn't find better words to describe it!) - I don't know about the form # (it's at home, I guess) but anyways, has a rectangular area where one signs - the signature is then used for the EAD (the EAD card has a signature section which appears to be taken from the signature card)