How do I make so that you only can have one of the same item? [closed]

I am making a obby where you need keycard to come through a door. I did that script great. But the problem is, I want it to be so that you can be more than 1 player in the server. So I made alot of keycards so that they will not run out (but I would like to have one that stays even though a person gets it) But now one player can take all :( How can I script it so that it stays when a player takes it? And how do I make so that yo can only have one of the same item? (I did not try to script that because I have no idea how)