this relates to an end closure for conventional types of containers which may be in the form of glass or plastic jars and bottles or in the form of specially formed metal containers having a folded outwardly projecting annular rim at the top thereof . the end closures are constructed so as to be snapped in place on the containers thus retaining the closures on and keeping the containers closed by a mechanical interlock between the respective closure and container . further , the end closures have heat - bondable surfaces which when subjected to low temperature heat , such as by heating the rims of the containers or by heating the packaged product within a retort cooker , the heat - bondable surfaces of the end closures will bond to the touching surfaces of the container .