1. First, draw the design of the gutter cornice mold on paper or computer software. Be sure to mark the position and size of 120 degree angle and right angle on the drawing. According to the design drawings, choose the appropriate materials to make the mold. The mold material can be wood, plastic, metal, etc. , depending on the actual demand and production capacity.

2. Secondly, according to the size and shape of the design drawing, use tools such as saw and cutting machine to cut the mold material into the required shape. Grind and trim the cut mold material to ensure that the mold surface is smooth and free of burrs and sharp edges. Assemble all parts of the mold according to the design drawings to ensure the structural stability of the mold.

3. Then use an angle measuring tool, such as an angle ruler or protractor, to test whether the angle of 120 degrees and the right angle on the mold are accurate. Make the gutter cornice line with the mold to see if the effect of the mold meets the expectation.

4. Finally, according to the test results, the mold is optimized and improved to ensure its function and effect are more perfect. Once the mold is made, it should be properly preserved and regularly maintained to prolong the service life of the mold.