Each year on the wonderful Feast of the Epiphany chalk is blessed at Church and people are invited to take some home and mark their homes with a prayer for blessing. The priests are also very happy to visit homes and do the blessing.
Seeing the marking at the door is a gentle reminder of God’s blessing, and a sign to all of a Christian home.
Using chalk either above the door, outside, or at the side of the door, outside or inside, the markings 20 + C + M + B + 13 are made, or (20+K+M+B). 20 and 12 being the year, C (K), M, B being the intitials of the traditional names of the wise men, Caspar, Melchior and Balthasar, they can also stand for Christus Mansionem Benedicat, the Latin words meaning, May Christ bless this home.
Or you may instead make a simple cross mark with chalk +
These prayers are used in our parish:
God of heaven and earth, you revealed your only Son to every nation by the guidance of a star. Bless this home and all who live in it. Fill us with the light of Christ, that our concern for others may reflect your love. We ask this through Christ who dwells among us. Amen.
Loving God, may all who come to our home this year rejoice to find the love of Christ here; and may we seek and serve, in everyone we meet, that same Jesus who is your incarnate Word, now and forever. Amen.
Here is a 2015 update about it.