Grille (cryptography)

Grille cipher is a type of cryptography, a way to take a message and turn it into a secret code. In a grille cipher, a message is written on a sheet of paper with a pattern of lines and holes. Then a piece of paper with the same pattern is put over it. To read the hidden message, someone would need to look at the paper with the pattern and use it to uncover the words in the secret message.