High Quality Content by WIKIPEDIA articles! An x mark (also known as a cross, x, ex, exmark or into mark) is a mark (x, ×, X, , , , , , etc.) used to indicate the concept of negation (for example "no, this has not been verified" or "no, I don't agree") as well as affirmation (for example in election ballot papers or in x marks the spot). It is often used opposite the checkmark (or the O mark used in Japan). It is also used as a replacement for a signature for a person who cannot write their name. Typically, the writing of an X used for this purpose must be witnessed to be valid. As a verb, to ex off/out or to cross off/out means to add such a mark. It is quite common, especially on printed forms and document, for there to be squares in which to place x marks, or interchangeably checks.