Measurements in metal layout are made from which of the following?

Measurements in metal layout are made from the reference line, reference edge, or center line because these points provide a consistent and standard method for ensuring accuracy in measurements and layout work. Using a reference line or edge allows for uniformity across the piece being worked on and enables the technician to replicate measurements precisely.

This method is critical in aviation maintenance, where precision is paramount to ensure structural integrity and safety. Establishing a reference point reduces the chances of error that can occur if measurements are taken from arbitrary points or varying locations on the metal. By adhering to a specific reference, all further measurements can be relative to that point, streamlining both the layout process and ensuring that all parts fit together correctly during assembly or repair.