The present invention is a golf swing training device which guides the golfer’s leading leg in an arc around the trailing heel, maintaining a minimum distance between the leading leg and trailing heel. The clamp includes a first rigid member having opposed ends, each end defining a passage extending therethrough, a second rigid member having opposed ends, each end defining a passage extending therethrough, and two pins of generally u-shape. The network server may translate between HTML or other code supplied by the client, in order to access a database serviced by the intelligence server in all its functionality. The type of the disc as well as difference between the disc and an object other than the disc are determined based on the detection signals from the optical detectors and the side switch. The cantilever oscillating frequency is far from an oscillation frequency where the cantilever is slow to damp, which enables the cantilever to quickly damp in accordance with a variation of a transient oscillation frequency after the probe comes into contact with the specimen, and allows the probe to follow the uneven surface state of the specimen. The material may be any fluid that dissolves the photochromic dyestuff material.