A mobile lifting device comprises a dismantlable frame mountedonwheels and supporting an elevated horizontal beam which projects out beyond the perimeter of the frame.
一种可移动的提升装置包括一个安装在轮上的可拆卸的框架,它支撑伸在框架外的一个提升的水平梁。
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A tablet engraved about 3000 B.C.E. provides the earliest known example from Sumer, a roofed boxlike sledge mountedon four solid wheels.