This is an easy one to one correspondence activity! I would tell Ollie (3) how many “lights” 1-10 to put on each tree. Then I wrote the numbers 1-10 on the clothespins, mixed all the trees up and he had to recount and match the number on the clothespin to the amount on the tree. He loved it (especially because they can stand up like real trees) and wanted to make more with different stickers so I just sat and kept cutting trees! This is also a great activity to practice subitizing for numbers 1-5!!