The document discusses different types of scales used for technical drawings. It begins by explaining that a reducing or enlarging scale is used to adjust dimensions of large or small objects to fit a standard drawing sheet size. The scale ratio is called the representative factor. It then describes various types of scales - plain, diagonal, vernier, and comparative - that are used to measure different units and precision of measurements. Specific examples are provided to illustrate how to construct plain and diagonal scales, calculate their representative factors, and indicate distances on the scales.