Draw a big shape on one of the sheets of card and cut it out. If you're making a Christmas advent calendar, you could draw a Christmas tree. What other shapes can you think of?

Then draw 25 small "doors" across the whole tree, starting with number 1 at the bottom and ending with number 25 at the top. Make sure that they're not too big and that they all fit on the tree. Why not make the last door for Christmas day a little larger?

Use a dark-coloured pencil to number your doors.