Yes I mean cardstock. In the UK we just call it card. It's only 1 layer then I coated it with resin to make it hard and tidied up the key slots with a file. I have a circuit board I could use but not sure if I will use it or not as I'm not going for 501st approval.When you say card do you mean cardstock? What do you mean by card? Is it just card stacked together until the shape of the keyslots are formed or is it something else? You're going for 501st approval, how are you going to make the circuit board part of the keyholes?