Applying the wet-out fiberglass layers can be a messy experience. Sometimes these wetout layers are pre-cut and need to be applied in a specific orientation to fit properly.
The following is part of the process used during the work from Model M1911
The dry 1808 fiberglass is cut relief-cut to allow for good lamination around features that might not allow it to lay down properly. Cutting is easier when the glass is dry, rather than when it is wet with resin. The glass needs to be removed and wetout with resin before final lamination. Placing an alignment mark helps to place the glass back in the same spot after it is wetout.
These alignment marks can be made on the dry glass with permanent marker. They show up on the dry glass as well as the wet glass, and will still be visible once the laminate has cured. Sometimes that is good, sometimes it is bad.
Alignment marks can also be placed on the original surface to allow for transfer of location information through the laminate.