A ruler on the other hand can be used to draw a straight line, check for flatness, and measure length. Typically measures in inches and centimeters to give a more accurate measurement. Wrap around rulers can be rolled up for easy storage. These rulers can be fitted to a length and width based on your needs. Two way flat end rulers will allow you to fold them up for easy storage and has measurements marked on both sides of the ruler. Rulers and straight-edges can be made from a variety of materials including: metal, wood, and plastic.