On May 5, 2001, approximately 1300 Pacific daylight time, a LET L-23 glider, N265BA, collided with a taxiway identification sign during the landing roll at Arlington Municipal Airport, Arlington, Washington. The certified flight instructor and his student were not injured, but the aircraft, which is owned and operated by the Boeing Employees Gliding and Soaring Club, sustained substantial damage. The local 14 CFR Part 91 instructional flight, which departed the same location about 55 minutes earlier, was being operated in visual meteorological conditions. No flight plan had been filed. According to the instructor pilot, the dual student was just about to land at the north end of the grass landing area, when he, the instructor, decided that it would be best to land further down the runway. Without advising the student, the instructor partially retracted the spoilers so that the aircraft would float further before touching down. With the spoilers partially retracted, the glider drifted long, touched down on the wet grass, and departed the end of the intended landing area prior to coming to a stop. After it slid off the end of the landing area, it crossed a taxiway and collided with a taxiway identification sign. According to the instructor, although the wind was a direct cross during the approach, after he partially retracted the spoilers, it seemed to switch to more of a tailwind.