In the animation below, we use a protractor to measure two angles. A protractor usually has two scales, starting at zero at opposite ends. The animation shows how to use both scales.
The two angles are vertical angles and this also verifies that vertical angles are congruent.
The animated diagram above shows how to use a protractor to measure angles. It shows how to measure two angles that are vertical angles and so should be equal in measure. It verifies that both the angles ∠LQK and ∠JQM are in fact equal.
For a description of the protractor see The Protractor
For a demonstration of using the protractor to draw an angle see Drawing Angles with a Protractor
The above animation is available as a printable step-by-step instruction sheet, which can be used for making handouts or when a computer is not available.