Fitting
Trying on a sample or a muslin to check how it fits and to mark the corrections to the pattern.
A fitting looks at balance, ease, lengths and movement, not just the circumferences. The corrections are noted on the pattern, a new sample is sewn if needed and the changes are recorded in the tech pack. In industrial work it is done on a fit model whose measurements match the base size, or on a dress form.
Example
At the fitting, the pants show wrinkles under the seat; the patternmaker lengthens the back rise and sews a new sample.