A three-piece can is a food can assembled from three separate parts: a cylindrical body formed from a flat sheet, plus a top end and a bottom end, all joined by seams. The body’s side seam is typically welded, and the ends are attached by double seaming — folding the metal edges together into a hermetic seal. The design is economical and versatile, used for everything from vegetables to pet food. Its vulnerability lies in those seams: any defect in the side weld or the double seams can admit microorganisms after processing, causing spoilage or, in low-acid foods, a botulism risk. Seam inspection — visual checks and destructive tear-downs — is therefore a critical quality control in canneries.