Abstract: An automatic fastening system is disclosed for use in fastening deck boards to stringers in a pallet-making machine or the like. The automatic fastening system of the preferred embodiment comprises an adjustable frame having a plurality of staple guns pivotably mounted on the frame and has automatic positioning means, in the form of a wheel, associated with each staple gun for positioning the staple guns by automatically raising and lowering the staple guns as the height of the pallet deck board changes and as the height of the pallet structure changes depending upon whether or not stringer-type pallets or block-type pallets are being manufactured. Also disclosed is an automatic firing pneumatic circuit for the subject fastening system for automatically fastening a plurality of deck boards to a plurality of stringers.