But instead of hustling a dollar here and a dollar there with deft openings and clever traps, the mostly homeless players and their supporters were playing Sunday in defiance of a recent police crackdown and ban on the public games. And they were backed by a brass band and several homeless advocates who helped organize the three-hour "chess-in" under bright, blue skies on a hot San Francisco afternoon.
Earlier this month, police confiscated chess gear, tables and chairs at the site.
Police said the games had begun to attract illegal gambling and drug sales to the area adjacent to a cable car terminal, which is a popular tourist destination. Nearby merchants had also complained about an increase in illegal activity.
"We don't mind the chess players and would like to have them back," said Cody Hunt, manager of an electronics store in front of which the games were played. "But lately, the games have attracted loud dice games and open drug deals, and nobody needs that."
The chess players argue that the police response to the illegal activity that took place near the games was heavy-handed and indiscriminate.
"Have the drug deals stopped because chess has been banned?" said Andrew Resignato, a San Francisco resident who would play a game along Market Street occasionally. "It was an excuse to move homeless people away from here."
San Francisco police didn't return a phone call Sunday.
Police Capt. Michael Redmond told the San Francisco Chronicle last month that he agreed the chess players themselves weren't the problem. But others used the games as a shield for illegal activities. Redmond said arrests and complaints from merchants increased in the area.
"It's turned into a big public nuisance," Redmond said. "I think maybe it's a disguise for some other things that are going on."
Hector Torres Jr., a homeless man who scratched out a living renting his chess equipment, tables and chairs to Market Streets players, said the games were a San Francisco tradition that attracted all sorts of players from all walks of life.
Torres and others said it's unclear whether regular games will resume in their usual spots, someplace else or disappear forever.
"Chess isn't a crime, and we aren't criminals," Torres said as he knocked over his king in resignation of a game. "San Francisco is about this kind of stuff. About diversity and differences. We just want to play chess."