Dab tsi yog saw hoist: Tes saw hoist yog ib qho yooj yim rau siv, yooj yim-rau- nqa phau ntawv nqa tshuab ' tuaj yeem siv rau hauv cov chaw tsim khoom tshiab, cov chaw nres nkoj, qhov chaw qhib cua tsis muaj hluav taws xob rau nqa cov khoom hnyav, tes rub hoists tuaj yeem ua tau. siv nrog khiav trolleys, taug kev ntawm I-beam thiab lwm yam tra...
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