Blessing of the moon, is a blessing said at the beginning of the Hebrew month. The Hebrew month begins in the lunar new moon (i.e. when the moon is completely dark), and to mark this event it is customary to say this blessing.
It is customary to say the "Kiddush levana" on the Saturday night closest to the beginning of the month. This blessing is said outside the synagogue, (one of the parts of the blessing is: "Just as I dance against you. And I can not touch you. So all my enemies will not be able to touch me badly," and it is clear that to dance in front of the moon, one must be outside).
For this reason, in many synagogues a sign is displayed with the blessing written in extra large letters, so that they can read, in the little light that exists during the birth of the moon. This is the reason why extra large letters are called in the Hebrew language - "Kiddush levana letters".
There are many versions of the moon’s blessing, according to the testimonies and customs that exist in Judaism. Among the Ashkenazim, the blessing of the moon is called - Kiddush Levana.
About the signs
There is no uniform format for these signs. It should be noted that in almost all the signs is at the bottom the names of the philanthropists, thanks to whose contribution the sign was erected