Fig 1: Trundle wheel with counter
A wheel used for measuring long distances.
Trundle wheels have been used for many years to measure long distances fairly accurately. Older units consist of a wheel and handle. The wheel has a small segment that comes into contact with the handle section making a clicking sound every metre that the wheel travels. By counting the clicks, the operator is able to calculate distances much easier than by using surveyor tapes.
Modern units may incorporate a counter which provides more accuracy and digital trundle wheels are very accurate.
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