To put it simply (and this may even be an over simplification) a set of hands carved and placed over a tombstone in a Jewish cemetery are called Kohen (or Kohain, or Kohanim ) hands, and represent a priestly blessing. The staff at MyJewishLearning.com explain that a kohen "is a descendant of the sons of Aaron who served as priests in the Temple in Jerusalem." Lorne Rozovsky at Chabad.org delves further: According to the Torah, Jacob had twelve sons. Each son was the founder of one of the twelve tribes of Israel. Each tribe had a separate territory, with the exception of the tribe of Levi. During the Exodus, when the Israelites made the Golden Calf, only the Levites refused to worship it. As a result, they were appointed servants to G‑d. Of the members of this tribe, those who were descended from Aaron, brother of Moses, became the kohanim . Aaron was the first kohen , and also the first high priest. The priestly blessing is a ceremonial prayer recited by the kohanim, wh...
Telling the Tales of Tombstones