Abstract: A lightweight, convenient training device includes a rigid, elongated member having first and second ends, and a clamping mechanism used to adjustably then rigidly secure the member at its first end to a golf club, including a putter, preferably to the shaft at a point just below the hand grip. So positioned, the second end of the member may then be comfortably positioned in the user's armpit to stabilize the swing, with the adjustability of the clamping mechanism ensuring compliance with various grip styles and lie angles. In the preferred embodiment, the elongated member includes a bend near the first end to prevent contact with the user's hands, and the clamping mechanism includes means for adjusting the elongated member along two degrees of freedom with respect to the golf club shaft.