1. The simplest convention is solid and dashed wedge formula in which 3-D image of a molecule can be perceived from two dimensional picture.
2. In this representation, a tetrahedral molecule with four atoms or groups a, b, c and d bonded to it can be represented by wedge formula as follows.
3. A solid wedge 
or a heavy line is used to indicate a bond projecting above the plane of the paper and dashed wedge 
or a dashed line is used to depict the bond below the plane. The bonds lying in the plane of the paper are shown by normal lines.
