Ride up to the obstacle at a slight angel with your feet in ollie position and your knees bent. Ollie up, and aim the trucks toward the edge of the obstacle. Try to land mostly on top of the obstacle with the wheels locked up against the edge. Grind to the end or until you're ready to come off. Shift your weight over the back truck, and push down on the tail, lifting the front truck off the obstacle. Use your momentum to get the back truck off the obstacle. Land, and roll away.