I think this was for 3rd Gen IPad note ruler dimensions in pictures and this is attached via 3 magnetic prongs in the side.
The Apple Smart Keyboard Folio for iPad is a sleek and functional keyboard folio case designed specifically for Apple iPads. Made from synthetic suede material in a stylish black color, this folio offers both protection and functionality. The Smart Case feature automatically activates the iPad's screen when opened, creating a seamless and convenient typing experience.
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