Cuatrillo
Cuatrillo is a letter of several colonial Mayan alphabets in the Latin script that is based on the digit 4. It was invented by a Franciscan friar, Alonso de la Parra, in the 16th century to represent the velar ejective consonant found in Mayan languages, and is known as one of the Parra letters.
A derivative of the cuatrillo by adding a diacritic,, was used for the alveolar ejective affricate found in the same languages.
As an example of use, the letter appears when spelling the name of the Kʼicheʼ language in the Parra orthography: ꜭiche.