The coplanar point is an optional property that can be supplied to constrain the  

set of planes containing the planar guides made by the implementation. If set,  

all guide planes will contain it. By default no coplanar point is set. This  

option is useful in conjunction with the coplanar direction option to define an  

axis contained by all guide planes. An example where such an axis is useful is a  

blend operation between involving a cone: The customer application might prefer  

that all guides planes to contain the cone axis.