What Has an Eye but Cannot See?

Why a needle fits

The eye of a needle is the small hole at one end where the thread goes through. The word "eye" there has nothing to do with sight, which is why the clue "cannot see" sounds like a contradiction until the second meaning arrives. The eye is small, and that is why tools called needle threaders exist.

Other things with an eye

The needle comes to mind first for most people, but it is not the only answer. A potato has eyes, the small buds from which new shoots grow. A hook and eye fastener has an eye, the loop that the hook catches. The calm center of a storm is also called its eye. Each of these has an eye and no sight, so each is a fair answer to the riddle as it is worded.

When a listener gives one of these, it is worth accepting before offering the needle.

Body words in disguise

Many riddles borrow a body word for an object. The page on a neck but no head does it with a bottle, and a clock with hands and a face would work the same way.