How long is a piece of string

 A piece of string's length depends entirely on how long it's cut! There's no set size for a piece of string. It can be anything from a millimeter long to kilometers long, depending on the situation.

The phrase "How long is a piece of string?" is often used as a humorous way to point out that a question is vague or lacks context. It's a way of saying "I need more information to answer your question."