Composite angles using Set Squares 

Another video on using set squares, but this time explaining how to draw composite angles. The angles that can be drawn are the 75 degree and the 105 degree angles.
One can also draw an angle of 15 degrees using the method explained, but it has not been included in this video to keep it simple. If you feel like a challenge, you can try and figure out how to do it by yourself though (Hint: It has to do with the sliding ruler).
If you decide on buying a pair of set squares (and you should), practice using them by drawing a few lines at those angles. Practice, practice and more practice to become fast and precise.