Profile gauges are used for copying existing profiles by direct measurement, the sliding pins are pushed against the profile to be measured giving the positive shape on one side and the negative on the other.
Invaluable when scribing into existing skirting or window frames for example; because you can simply record the profile and take it to the bench rather than grovelling about on the floor or trying to saw at the top of a ladder.
As you would expect, the Japanese made Shinwa is a very good example of its type, with 1mm stainless steel pins that move smoothly but firmly into position.
