| 摘要 |
Two separate containers are secured together by their respective bottoms. One container has a cavity in its bottom which has an annular frictional shoulder. The other container has a protruding shoulder on its bottom comparable in size to the cavity on the other container. That shoulder has an annular recess therein adapted to engage frictionally the annular shoulder in the other container. The cavity in the one container and the protruding shoulder on the other are of oval shape.
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