The glider was substantially damaged when it impacted terrain during an approach to land. The certified flight instructor (CFI) stated that the glider was towed to 2,000 feet above ground level (AGL) before releasing from the tow plane, after which soaring maneuvers and turns were performed. The glider then entered the traffic pattern at 1,000 feet AGL. When the glider turned to the base leg, the CFI noticed that it was "above glide path" and he performed 360 degree turns to lose altitude and "give time for second glider to launch." The CFI stated that while on final approach the glider rolled "abruptly" to the right at approximately 80 degrees of bank and began to descend. The CFI recovered just above the ground and then noticed that the glider was heading toward a fence line. The glider was able to climb over the fence and began a turn toward the airport. The pilot reported that the glider "stalled" and impacted terrain as he attempted to maneuver the glider over a second fence line.