It is a tradition in the Catholic Church to bless chalk at the Masses for Epiphany, then use the blessed chalk as part of blessing one’s home in the New Year.
To do this blessing at your home, use the blessed chalk, which will be available after the Masses on January 4/5, to write the following above a doorway in your home:
20+C+M+B+25
As you are writing, pray the following prayer:
Lord our God, bless this household. May we be blessed with health, goodness of heart, gentleness, and the keeping of your law. We give thanks to you, Father, Son, and Holy Spirit, now and forever. Amen.
There are 2 meanings for C, M, B
Caspar, Melchior, & Balthasar (the 3 magi) or
Christus Mansionem Benedicat which in Latin means May Christ Bless This House
The “20” at the start and “25” at the end is the year of the blessing, and the “+” signs represent the cross