My scale will not balance at zero.

Place both the large and small poise on zero (make sure both poises are in the zero notches all the way to the left shoulder of the beam). To balance the beam at zero, turn the adjustment screw to the left of the beam counter clockwise to raise the beam pointer or clockwise to lower the beam pointer until beam is floating freely in the center.

Or:

Check and make sure the scale was put together properly. Lay the scale on an angle where the base is hanging free. Make sure the steel rod is securely hooked to the nose iron underneath the base. (See photos in your instruction manual.)