In canning, a defective seam where the tinplate edges have not been properly joined, whether by soldering in older cans or by double-seaming in modern ones. A loose seam compromises the can’s hermetic seal, allowing microorganisms to enter and spoilage or food poisoning to develop, and it may permit leakage of contents. Seam integrity is one of the most critical quality checks in canneries: operators routinely cut open sample cans to examine seam cross-sections under magnification. Any batch showing loose seams is rejected or reworked. The term underscores that a can is only as safe as its weakest seal.