Use. Three views are orthographic engineering drawings reflecting the length, width and height of an object. Three views need to be dimensioned, because only by dimensioning can we know the size, tolerance and supplementary explanation of each part. In addition to the dimensions, the three views should also be marked with roughness, shape and position tolerance, local amplification, etc. In addition, the technical requirements, the use of parts materials, heat treatment methods and subsequent hardness requirements should also be stated; Finally, fill in the title bar, including name, code, material, quantity, proportion, signature, etc.