| 摘要 |
A stepped structure (100) comprising a plurality of separate run portions (1), wherein at least one of said plurality of separate run portions (1) comprises upper and lower sheets (20) each sheet having a forward longitudinal end portion (14, 24) bent downwards and a rear longitudinal end portion (12, 22) bent upwards, and a core material (30) between said upper and lower sheets (10, 20).
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