the end walls forming the bottom or upper wall

Full Title

Bundles of articles held together by packaging elements for convenience of storage or transport, e.g. portable segregating carrier for plural receptacles such as beer cans, pop bottles; Bales of material > Bundling wrappers or trays > Shape of the formed wrapper, i.e. shape of each formed element if the wrapper is made from more than one element > tubular with end walls, e.g. walls not extending on the whole end surface > the end walls forming the bottom or upper wall