Abstract: A container and closure cap therefor which forms a package unit, with the container having an open top, a continuous sinuous surface adjacent the open top, the sinuous surface including rounded projections merging into adjacent rounded recesses, a closure cap for the container, the cap having a skirt and an open bottom with a continuous sinuous surface on the skirt, the last mentioned sinuous surface shaped complementary to the container sinuous surface so that the sinuous surface of the closure cap is adapted to engage the container sinuous surface with the projection of one positioned in the recesses of the other when the closure cap is in closing position, one or the other of said closure cap and container having an annular wall portion offset inwardly of its respective sinuous surface and adapted to interfit within the other of the closure cap or container adjacent its sinuous surface to frictionally secure the closure cap to the container.