Glide plane - A reflection by a mirror plane followed by a translation parallel to the mirror. A glide plane is designated by “a”, “b”, or “c” if the translation is ½a, ½b, or ½c and by “n” if ½(a+b), ½(a+c), or ½(b+c), i.e., along a face diagonal. An a-glide can be perpendicular to the b- or c-axis; a b-glide can be perpendicular to a or c; a c-glide can be perpendicular to a or b; and, an n-glide can be perpendicular to a, b, or c.

There is also a “d-glide”, which is characterized by a translation of ¼(a+b), ¼(a+c), or ¼(b+c).