Caps are closures fitted to bottles, jars, tubes and other food containers to seal and protect the contents. They range from screw caps and crown corks to tamper-evident and child-resistant designs, made from metal, plastic or composite materials. A good cap maintains hermeticity, preserving freshness, preventing contamination and moisture exchange, and showing clearly whether the package has been opened. Cap application and seal integrity are critical control points in packaging lines, since a faulty closure can compromise the safety of the entire product.