Who can help me to explain the second grade congruent triangle "ruler and gauge drawing"

Who can help me to explain the second grade congruent triangle "ruler and gauge drawing"

It's my pleasure to answer your question. Is your question "to make a triangle congruent with a known triangle"? If it is, the method is as follows: 1. Set three fixed points of a known triangle as a B C. 2. Draw a straight line at will. 3. Cut the length of ab side of a known triangle (note that the radian of the circular gauge should be greater than cab). 4. Draw an arc with B as the vertex BC length, 5. Connect these three points to form a closed triangle. 6. Name the new triangle (be careful not to repeat the letter with the known triangle, let it be the triangle XYZ). 7. Write the conclusion: that is, △ XYZ is the result. The proof is completed. Principle: SAS