STEP 2: Centre the protractor on the same end of the line and make a dot at 40°. From the same end, use a ruler to draw a line through the dot, crossing the arc.

Save $50 on a tool that functions as a floor plan scanner, ruler, protractor, and more Change your DIY projects forever.

Make a mark where the 50° is on the outside scale. Step 4: Remove the protractor. Using a ruler, join the mark you made to the end of the line that was in the centre of the protractor.