“Rattrapante” is a French term that denotes the split-seconds hand of a chronograph. This additional seconds hand can be stopped independently of the chronograph hand and resynchronised with it at will.

Initially, both hands are directly superposed so that only the rattrapante hand is visible. When a measurement is started, both hands begin to run together and the chrono sweep-seconds hand remains concealed. It only becomes visible when measurement of the first event is stopped. At this point, the rattrapante hand stops while the chronograph hand continues to measure the elapsed time. It, too, stands still when measurement of the second event is stopped. This allows for the comparison of two time measurements with the same start time, such as the lap durations of two runners.

A further function is available if the chrono sweep-seconds hand is not stopped: Pressing a button realigns the stopped rattrapante hand with the chrono sweep-seconds hand; both hands will then run together until the rattrapante hand is stopped anew. It is a process that can be repeated any number of times. This makes it possible to measure one aggregate time and several lap times – for instance, the individual lap times of a horse in a race and its total time.

By cleverly combining the functions of the chronograph and rattrapante mechanism, many comparative measurements can be performed relative to a reference time. A rattrapante chronograph can even measure minima and maxima, such as the fastest or slowest of many laps.