What is the name of the item on a dual dimensioned drawing that indicates how dimensions can be identified?

In a dual dimensioned drawing, the item that indicates how dimensions can be identified is commonly referred to as a "note." A note serves as a textual reference or instruction in the drawing, providing details that clarify the meaning or method of interpreting the dimensions shown. It may include specific information about measurement systems, tolerances, or any unique conventions used in the drawing that would assist the viewer in understanding how to read the dimensions accurately.

This type of guidance is crucial in ensuring that anyone who examines the drawings can clearly understand the intent of the design without ambiguity. Hence, notes are essential for conveying important details that may not be evident solely from the graphical elements of the drawing.