Using only hand tools, I made a groove for a wedge and the wedge does not fit tight and perfect. How do I highlight where the exact point is that needs to be reworked? I've seen someone using carbon paper or some other compound but that cannot work with a wedge. In another words how do you mark gaps, to highlight tolerances and so on?
Another example, I have a curved piece of wood and I want to make another piece of wood fit to the curve perfectly. Again how to highlight any gap or wood excess? I know I can use light but there are certain cases where you cannot use light.