1 cm H dot DMEGA do de de de zig normal 119 160 DMEGA Figure 13. Drawing the normal line on the top portion of the outline of the refraction block. 1. Draw and label a diagonal line from the intersection of the normal line at a 30* angle. Refer to Figure 14. 1. Line up the protractor with the normal. 2. Mark a dot 30' from the normal. 3. Use the straight edge of the protractor to connect the dot at 30' to the point where the normal intersects the block outline