Wireline extensometers are very simple devices that are quite commonly used. Their principle is simple: A weight is suspended against a measuring scale by a wire that goes over a pulley and is attached to a distant mounting point. The mounting point would be installed on the potentially moving area, where the base (which includes the scale, weight, and pulley) would be installed on solid ground. Movement of the mounting point translates to the suspended mass moving against the scale. While this technology is not ideal for many situations, it is simple and accepted.