Which of the following is NOT a method used in forming sheet metal?

Shaping is not traditionally recognized as a distinct method of forming sheet metal in the same way that the other options are. Stretching and shrinking are both techniques that manipulate the material to change its shape while maintaining its overall thickness. Stretching involves elongating the metal to create curves or forms, whereas shrinking compresses specific areas to create concave shapes or details.

Crimping, on the other hand, involves bending the edges of the metal to join two pieces together or to create a specific profile, often used in ductwork or in automotive applications.

While "shaping" may be included as a general concept in metalworking, it doesn't refer to a specific, recognized method used for forming sheet metal akin to how stretching, shrinking, and crimping are categorized. Thus, identifying shaping as the option that does not align with the recognized methods of sheet metal forming is appropriate.