The GREEN GLASS DOOR riddle?

in order to go in the green glass door, you have to bring something.
“i’m going to the green glass door and i’m bringing Jelly, and i can go in.
but i can’t go in with jam.
i can go in with a ball
but i can’t go in with a square

… so what are you going to bring to the green glass door that will let you in? don’t say why just say what you’re going to bring and i’ll tell you if you can come in or not.