Trouble with GUI above or under

[Memelife_remade]

So I’m making this GUI but I can’t figure out how to make 2 GUIs to go under one or the other.

For example, how do I make that white square go under the green rectangle? It keeps going above it.

[DecodedMint (mint)]

Increase the ZIndex property of the green button.

[Memelife_remade]

Thanks a lot! It works now.