A screw jack, also called a top jack or oil jack, is an adjustable accessory for scaffolding and formwork support systems. It mainly consists of a screw rod, a nut, and a tray, and is divided into upper jack and lower jack. It is generally machined from Q235 round steel, with neatly rolled threads for smooth adjustment and stable load bearing. The tray is firmly welded and not easily deformed, and the surface can be painted or galvanized for rust protection. During construction, it is placed at the upper and lower ends of steel pipe frames to fine-tune the support height and balance the load. It is widely used for formwork support in building construction, bridges, and basements, and can be reused repeatedly.