Anchors and a marking symbol.
A person may notice rocks on some Jewish gravestones. They are set on top of the burial monument rather than written in it. Some believe they are reminiscent of the period when gravestones were marked by mounds of stones. People would carry a rock to replace a stone because it may be removed or worn out. Some believe that the rocks on the gravestone represent a method for the soul to remain near to the body. Rocks were also placed on graves to alert Jewish priests to the presence of a corpse, preventing them from approaching too closely and rendering the body unclean.