placing stones

"Typically, even when visiting Jewish graves of someone that the visitor never knew, he or she would leave a small stone at the graveside. This shows that someone had visited, and represents permanence. This contrasts with the common custom of leaving flowers, which do not live long. Another reason for leaving stones is tending the grave. In Biblical times, graves were marked with mounds of stones, so by placing (or replacing) them, one perpetuated the existence of the site."