A protractor is a handy mathematically circular or semicircular tool which allows you to measure an angle or draw/constructing an angle of a specified measure.  Using a protractor is simply and straightforward you just need to ensure that you line it up correctly.

A protractor marked with degree measurements. The straight edge is generally marked with centimetres or inches, and can be used as a ruler. The curved portion will tell you the measurement of the angle. Here's how to use a protractor 

To Measure an Angle
- Find the center hole on the straight edge of the protractor
- Place the hole over the vertex, or point, of the angle you wish to measure
- Line up the zero on the straight edge of the protractor with one of the sides of the angle
- Find the point where the second side of the angle intersects the curved edge of the protractor
-Read the number that is written on the protractor at the point of intersection. This is the measure of the angle in degrees 

To Draw/Construct an Angle
- Use the straight edge of the protractor to draw a straight line. This line will form one side of your angle
- Find the center hole on the straight edge of the protractor
- Place the hole over one end point of the line you have drawn
- Line up the zero on the straight edge of the protractor with the line
- Make a mark at the number on the curved edge of the protractor that corresponds to the desired measure of your angle. For example, mark at 90 for a 90-degree angle
- Use the straight edge of the protractor to connect the mark to the end point of the first line, forming an angle

To Draw/Construct Lines
The straight edge of the protractor is used often to draw lines especially when marking and drawing an angle and when measuring the size of angles. The ruler acts as a guide in this case. The protractor is used to draw dots at the points where one needs to have their angles and to join the dots marked in a straight line..

See UK Office Direct’s range of Set Squares and Protractors