Clock and watch making in the mid-fifteenth century can be considered a new trade in Europe. Although instrument making can hardly be considered a trade at all, the two occupations were intertwined – despite which the multi-faced, hard-to-define, small-scale nature of instrument making would mean that, unlike clock making, it would never become incorporated as a recognised trade. The two had developed together from the mid-thirteenth century onwards, when a new semi-autonomous mechanism, controlled by a falling weight for sounding bells, was combined with displays that presented visually not only the hour, but also the place of the Sun and Moon in the zodiac, the rising and setting of the signs, the length of day and night, the seasons, and, more rarely, the movements of the planets. The development of an alternative motive force – the controlled unwinding of a coiled spring – in the early to mid-fifteenth century made possible the introduction of a new range of portable and personal timekeepers, but many of them still offered calendrical and astronomical indications. At the same time, sundials were essential for setting any mechanical timepiece should it stop, and for checking the (often variable) time it showed against that given by the only available standard – the movement of the sun. The making of sundials therefore became associated with clock making.