You will find it is also great for aligning pieces of wood together, making sure a factory cut is correct. Checking door frames or cabinet installation for square. Also a great tool for laying out stair stringers.
You can mark out a diagonal line of any degree from 0 to 90. Using guide stops will help if you need to make multiple cuts of the same angle.
Here is a demonstration of some great uses for your speed square.
The speed square comes in standard 7 inch and also 12 inch for bigger projects.