Where can topstitching be observed on a garment?

Topstitching is a decorative and functional stitch that is typically applied to the outside of a garment. It serves both an aesthetic purpose, enhancing the design of the piece, and a practical function, providing strength and structure to seams and hems. When a garment has topstitching, it is usually visible on the surface, highlighting its style and design elements, such as along the seams, collar, or pockets.

In contrast, topstitching would not typically be found inside, as that would negate its decorative aspect. On the hem, while it is possible to apply topstitching, the term "outside" more broadly captures the general location where topstitching is most commonly applied, as it is intended to be prominent. Lastly, the lining of a garment is often hidden from view and typically does not feature topstitching, which is designed to be seen. Therefore, the most accurate answer regarding where topstitching is observed on a garment is indeed the outside.