Scored criss-crossed lines or grids are commonly found in churches and early houses.
These marks are often quite irregular and are believed to have had an apotropaic function, perhaps being seen as a trap or barrier. Common locations appear to be door and window openings and on doors themselves. Examples have been found in houses where the marks are on the back of the door to, for example, a dark roof space, presumably with the intention of stopping any malign forces passing from the roof into the house.
