Measure the sides with your protractor or a ruler. If the first line you measure is the same length as the line across from it and the remaining two lines are of equal length, your quadrilateral should be classified as a parallelogram.
Use the protractor to measure the angle of any corner between two of the lines. Classify the object as a parallelogram if the opposite corner has the same angle as the first corner and the two remaining corners are also equal angles. The total number of degrees of any two neighboring angles will also add up to 180 if you wish to further verify that your object is a parallelogram.
Draw or create a line that goes diagonally from one corner to the other. Make a second diagonal line to connect the remaining corners. When the two lines intersect, classify the quadrilateral as a parallelogram if they also bisect each other. This means that the lines will cut each other perfectly in half. Measure the both sides of one line to make sure they are the same length. Do the same for the second line.
Determine if the shape is a square or rectangle. It should be classified in the larger category of parallelograms as well.