In old times people often carved symbols near doors/ entrances to denote certain things.
It was sort of a secret code.
"Here we feed the vagrant"
"Here we are protestant"
"We know witchcraft"
Thieves and miscreants also used a code, but these were made on less noticable places.
"Careful, dogs"
Etcetera.
It is very likely that these signs note allegiance to a faction.
Edit, to poster above:
Oo interesting