a food container made of thin plastic sheet material comprises bowl and a lid , each having a peripheral sealing region with a downwardly facing channel generally shaped like an inverted “ u ”. the outward edges of the channels are lockingly engaged . the channels mate and engage to form a primary seal at a conical interface and a secondary seal at a rib . the rib may be on either the base , the lid , or both . leverage provided by elastic forces in the lid &# 39 ; s channel tightens the seals .