There are two main difficulties in studying molecular symmetry of dihedral point groups. One is locating the C[subscript 2] axes perpendicular to the C[subscript n] axis, while the other is finding the s[subscript]d planes which pass through the C[subscript n] axis and bisect the angles formed by adjacent C[subscript 2] axes. In this paper, a method of learning to draw 2D projections has been proposed to identify symmetry elements. Molecules with similar projective polygons are also compared to discuss the differences in point groups.