Abstract: A sprinkler for watering an area having a specific shape using water subject to an intermittent and regular variation in pressure introduced against a patterned plate positioned in the base of the sprinkler. The plate is situated adjacent to a slotted opening in the lower solid side of a hollow head moveable under water pressure within a cavity formed between the base and a cap of the sprinkler. A nozzle is attached to the upper end of the head to distribute the water passing the restricting window and segment of pattern disposed in its path in the base. Springs are associated with the head to provide a torque to the sprinkler head as the head rises in the cavity under pressure of the water on the lower side of the head. A gear and ratchet is provided on the head to prevent the head from returning to the first position upon reduction of the water pressure and resultant reaction of the springs to return the head to its position of rest within the cavity.