Larwyn wrote:.... it would matter little if your tape was a few centimeters or fractions of an inch off, just so you make your parts to fit....
When drawing the hull shape of a ship back in the dark ages (around the time I learnt), there was often a need to acurately transfer dimesnions from one part of a drawing to another. This was done using 'tick strips' - a strip of paper laid along the measurement you wanted to take. Add a pencil mark ('tick') at each end of the object (you did not draw one tick first and then try to align the tick strip - innaccurate), move the tick strip to where you wanted the measurement and use the ticks to mark the new points.
The old guys who had some experience reckoned they could get dimensions within 10 thou of the original! That seemed a bit far-fetched to me, but getting within 50 thou (0.05") is easy.
Andrew