Constructions involve drawing various geometric figures using only a compass and a straightedge.  Rulers, protractors and other measuring tools cannot be used.  It is very important when doing constructions to use the special marks that indicate right angles and congruent segments and angles. 

Constructions provide greater insight into geometric concepts and provide tools to draw objects when direct measurement is not appropriate.  The following constructions show arcs drawn by the compass.  It is important to remember that the arc is part of a circle.  The compass is used to draw circles and therefore the width of the compass represents the length of the radius of the completed circle.  The full circle is not always needed to complete the desired construction.