On this page you can see some protocols for technical patterns and grading of garments in 1:4.
The pattern of a design is measured, prepared and drawn in order to create industrial pattern which contains all information for the seamstress to sew the garment in a very quick and rational way.
That way the garments can also be re-produced very easily. In order to do this, the procedure for the design of the patterns and the final elaboration of the technical garment must be followed correctly. Grading on the other hand is the procedure which creates the same technical pattern in different sizes. Hereby you calculate the difference of the sizes in millimetres (mm) with the help of measurement tables.
You need expertise and an excellent eye to change the pattern with the help of complex rules and distribute the difference in millimetres across different body shapes.
It takes years of experience to perfect this technique. I would even call it an art in itself.