Walls and doorways serve as literal and metaphorical canvases at Southern Exposure's first exhibition of 2008 -- a fitting tribute to the gallery's new space. "Four Solo Exhibitions" offers works by four Bay Area-based artists: Jenifer Wofford, Chris Bell, Elaine Buckholtz, and Bruce Tomb. With her sculptural installation and wall painting, Unseen Forces, Wofford reimagines the ubiquitous metal detector as a gateway not to security but to the unknown, a threshold to the unexpected. Buckholtz sets up a different kind of gateway, luring passersby from the street with her Scenes for a Box Carnival, which projects pulsating images onto the gallery's 14th Street exterior, trees, and sidewalk. Inside, Bell's video installation, Slow Pan Interior, plays with perception by projecting the gallery's walls back onto themselves, with a subtle time shift to throw the viewer off balance. Meanwhile, artist and architect Bruce Tomb presents his documentation of the wheatpaste posters on the "art wall" at Valencia and 24th Streets. Tomb, who owns the art wall building, has set up a website called the (de)Appropriation Project Archive (www.deappropriationproject.net, set to launch today), that allows viewers to compare the wall's various stages through the years and to peel back and reconstitute layers.