Pigpen

Pigpen places letters in “#” and “X” diagrams, then uses the nearby lines and dots as the symbol for the encoded letter. This comes in two main varieties.

It goes by a lot of names - the Rosicrucian cipher, the Freemason’s cipher, the Napoleon cipher, the tic-tac-toe cipher - and they are all this one cipher.

The Knights Templar get the credit too, but the cipher attributed to them is a different one: twenty-five symbols cut out of a cross pattee rather than out of grids. It is not on this site, because the charts that circulate for it disagree with each other and none of them traces to a medieval source.