Horizontal supporting device suitable for processing shell with U-shaped structure, and installation method

The invention provides a horizontal supporting device suitable for processing a shell with a U-shaped structure, and an installation method. The horizontal supporting device is formed by a supportingbase, two glue holding blocks, two telescopic rods, a plurality of locking screws and two fine adjusting rods, wherein shoulder through holes are formed in two sides of the top part of the supportingbase; locking screw installation holes and fine adjusting rod installation holes are formed in side walls of the shoulder through holes; one telescopic rod is inserted into the should through hole onone side of the supporting base; the outer end of each telescopic rod is fixedly connected with one glue holding block; racks are arranged on side walls of the telescopic rods; the end part of each fine adjusting rod is of a gear structure; and after the fine adjusting rods stretch into the fine adjusting rod installation holes in the side walls of the shoulder through holes of the supporting base, the fine adjusting rods c