Chalking the door

Chalking the door is a Christian Epiphanytide tradition used to bless one's home. It is normatively in the pattern of four crosses positioned in between the traditional initials of the three wise men, which are surrounded by the first two and last two digits of the current year (e.g. 20 ✝ C ✝ M ✝ B ✝ 25). The practice of chalking the door originated in medieval Europe, though it has spread throughout worldwide Christendom.