Dashed and solid wedge line notation

The dashed and solid wedge line notation is a method of conveying a three-dimensional perspective to a structure plotted in a plane. 

There are two common variations on this notation. Sometimes, at the chiral centre, only three bonds may be shown, two of which are of normal thickness, while the third is either dashed or a solid wedge the fourth bond is to a hydrogen atom, and is not shown for it is assumed to be orientated as necessary to complete the usual geometry of the chiral centre. In the other common variation, three bonds to the chiral centre are represented with lines of normal thickness, and only the fourth uses a solid wedge or dashed line to indicate the stereochemistry. Neither of these variations are as clear as the normal version. 

The structure at the far right above uses the dash-wedge notation to indicate three dimensions. A solid wedge indicates that a bond projects out of the paper toward the reader. A dashed bond indicates that it projects behind the paper away from the viewer. Ordinary lines represent bonds in the plane of the paper. The dash-wedge notation is an important and widely used tool for depicting the three-dimensional structme of molecules. 

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