A weight is placed on the machine's lever. To achieve a certain tension, the weight is moved to a specific location on the lever (the reading is taken from the left of the counterweight). The string is attached to a clamp at the base of the lever. The lever is then tilted to pull the string. To reach the correct tension, the lever must be in a horizontal position.
For a number of reasons, manual stringing machines are not recommended for professional use. The most significant problem is that the exact tension is only achieved when the resting weight is in a horizontal position. However, manual stringing machines are perfect for personal use and will quickly pay for themselves.