On August 16, 2003, at 1105 central daylight time, a LET L-13 Blanik glider, N302SL, piloted by an airline transport pilot, sustained substantial damage when it overran runway 36 (2,692 feet by 200 feet, dry turf) and subsequently collided with a road embankment at Highland-Winet Airport (H07), Highland, Illinois. Visual meteorological conditions prevailed at the time of the accident. The solo-instructional flight was operating under the provisions of 14 CFR Part 91 without a flight plan. The pilot did not report any injuries. The local flight departed H07 at 1040 and was returning at the time of the accident. According to the pilot's written statement, he was obtaining flight instruction for the addition of a glider rating and the accident occurred during his first solo flight. The pilot stated the flight was uneventful until he turned onto final approach. The pilot reported that he was high on final and had to slip to loose altitude. The pilot stated that during the slip the glider had "picked up some airspeed." The pilot reported that the glider landed "long, fast, and as a result hit the mound at the edge of the airport perimeter dirt road." The pilot stated that several witnesses recalled not seeing the spoilers deployed during the final approach and landing. The pilot surmised that he had mistakenly repositioned his hand on the flap lever and as a result had been raising and lowering the flaps instead of the spoilers.