| 摘要 |
The apparatus comprises at least two platforms which are positioned on one another, the dimensions of a platform located at a lower level being larger than those of a platform positioned on top of it. The platforms are preferably positioned concentrically on top of one another. The platforms may be round, square, triangular or oval. If appropriate, an intermediate component may be accommodated between a platform located at a higher level and a platform located beneath it, in order to change the difference in height between the two platforms.
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