There are hardcore swing aficionados out there, men and women for whom swing dancing is more serious business than retro lark. If you don’t know what you’re doing, get off the floor. When the swing craze swept through the Bay Area about seven years ago, you didn’t know whether to envy these swingers’ sudden position atop the apex of cool, or watch in amusement as they bitched about the amateurs crowding the clubs and asking, “Was ist das swing?” Now that the swing thing has shot its wad, and trend-chasers have moved onto to fresher fads (Lawn darts? Shuffleboard? Huffing?), the downside to culling the herd is the near-extinction of that once-proud species, the swing club. Sure, Ashkenaz still brings in Lavay Smith and her Red Hot Skillet Lickers a few times a month, but for regular zoot suit types, the only consistent venue for their sweaty pastime is the Two Left Feet Dance Hall in Danville. Two Left Feet offers traditional swing on Wednesdays, but the clear crowd favorite is West Coast swing, a slower variation that one can do to all forms of music, from rhythm and blues to doo-wop and even (cue horrified shudder) ‘N Sync. If slow, panty-exposing cartwheels to “Bye Bye Bye” is your thing, head on down to Two Left Feet on Friday, Saturday, and Monday nights.