Abstract: A stay rod connects a power end to a fluid end of a high pressure well service pump where the pump has a pump motor face on a power end which is spaced apart from a joining face of a fluid end by the stay rods. The stay rods each have an elongated unitary body having first threaded end which is sized to be received in a mating threaded opening provided in the motor face of the power end of the pump and a second opposing threaded end which is sized to be received in a mating opening provided on the joining face of the fluid end of the pump. The intermediate portion is of a greater relative diameter than either of its first and second threaded ends and is provided with a series of elongated flats which begin at the approximate juncture between a shoulder joining the second threaded end and extending in the direction of a shoulder joining the first threaded end. Each flat forms a torque surface for engagement by a torque wrench for torquing and installing the stay rod.