There is provided a container having both male and female sealing regions disposed
about its periphery in a pattern making it possible to seal a container with another
container having substantially identical sealing regions. The male sealing regions
used in the practice of the present invention may take the form of a U-shaped ridge
which is undercut along at least one leg of the U in a radial direction. Typically,
a container will be thermoformed from lightweight thermoplastic material giving
the U-shaped ridge considerable flexibility. The female sealing regions used in
the practice of the invention may take the form of an undercut channel adapted
to receive and match the undercut U-shaped ridges found in the male portion of
the container wherein the walls and base of the channel are sufficiently flexible
that the undercut portions of the U-shaped ridge are urged into engagement with
the undercut portions of the channel. Transition regions between the channels and
ridges have arculate undercut profiles to further seal the container. The containers
are further provided with asymmetric stacking features and inclined separator tabs.