As part of fixing my rudder damaged trailing edge, I went to build a template with dimension mentioned in the by law - with a small front leading hook similar to the keel template one.

The catch is that the template is at the minimum legal dimension. A +2mm thick (probably more for mine) profile, like my current rudder, does not fit -at all- in the template.

How can a template calibrated for minimum size be used to measure a legal profile that does not fit at all in it?

Could it be that the measurer has template with the max allowed size rather?
Sorry for the naive question - first time I am playing with template...
Cheers,