First off, let me say, this game is very dangerous & probably illegal! I don't recommend finding this and actually playing it... This is just for nostalgic purposes.
They have safer plastic models: (from Canadian tire in Canada)
Lawn darts (also known as Javelin darts, jarts or yard darts) is a lawn game for two players or teams. A lawn dart set usually includes four large darts and two targets. The game play and objective are similar to both horseshoes and darts. The darts are similar to the ancient Roman plumbata. They are typically 12 inches (30 cm) long with a weighted metal or plastic tip on one end and three plastic fins on a rod at the other end. The darts are intended to be tossed underhand toward a horizontal ground target, where the weighted end hits first and sticks into the ground. The target is typically a plastic ring, and landing anywhere within the ring scores a point.