This characteristic makes it possible to represent the locus of any chosen point of a planar mechanism in its true size and shape on a single drawing or figure. The motion transformation of any such mechanism is called coplanar.

• 有了这一特点,就能够在单个图或图形上以实际的尺寸和形状来绘出平面机构的任意位置的轨线。这种机构的运动变换称为“共面”。