Look for some sad faces among the thousands around town who used to cross the busy Harvest Road-Black Avenue intersection on the way to Walnut Grove Elementary and Harvest Park middle schools. Pleasanton's longest-serving crossing guard Sherrill Hamilton is stepping down today after 18-1/2 years on the job, the last 16 at the same corner. Married for 41 years to Roy Hamilton, the couple grew up in Pleasanton and lives in the same yellow-painted historic house on St. Mary Street which Roy moved into with his parents in 1949. The house was built in 1901 by the Orloff family, which owned the Orloff Dairy where Walnut Grove is now located. Grandson Tom Orloff, who is now Alameda County District Attorney, is Roy Hamilton's childhood friend.