This is a sign. General designers find some small mistakes after drawing, and they will make manual corrections. After the change, they will mark @ next to it, and then write down the mark, tag number, division, changed document number, signature and date in the schedule.

Mechanical drawing: Mechanical drawing is a subject that accurately expresses the structural shape, size, working principle and technical requirements of machinery with drawings. Drawings are composed of figures, symbols, words and numbers. They are technical documents that express design intentions and manufacturing requirements and exchange experiences. They are often called engineering languages. In addition, mechanical drawing is also one of the basic compulsory courses for mechanical and related majors in most colleges and universities. The reference books on mechanical drawing mainly include Mechanical Drawing published by beijing institute of technology press and Peking University Publishing House.