| 摘要 |
<p>The screw type jack is used for levelling scaffolding work and has a one-piece forged body. This has a wide base, its underside being concave and having lugs to grip firmly on the surface of the ground. The upright portion is threaded (2) to within a short distance (3) of the base and a nut (6) is screwed on. This nut supports the scaffolding tube (8), or an extension piece, its height being adjusted by a tommy bar (7). The hole (9) in the side of the jack enables fixing to prevent inadvertent movement and similar holes (2) in the base permits use of fixing bolts.</p> |
