Mount a large dildo with a flanged base to the front bumper of your car using bungee cords or tie-down straps to secure it. Or use a dildo with a suction cup base and apply it directly to the bumper. Step up onto the bumper and plant your feet wide on either side of the dildo, leaning forward onto the hood for balance and support. Lower yourself onto the dong, insert it, and bounce up and down. When you're done, remember to remove the dildo from the bumper, unless you want to attract attention while driving.