A method of assembling a deck board by using a step clip fastening device is disclosed. The method comprising the steps of fastening the step clip fastening device onto a joist by using a plurality of fastening tools; sliding a first end of the deck board into an inner cavity of a step clip attached at a first end of the step clip fastening device; and snapping a second end of the deck board into an inner cavity of a corresponding step clip facing the step clip attached at the first end of the step clip fastening device to form a mating relationship between the deck board and the step clip fastening device.