These lines or ridges, four in number, represent the locations of the intervertebral discs that separated the five sacral vertebrae. As ossification occurs at these sites the bone forms prominent ridges that demarcate the body regions in-between. The ridges end laterally in the sacral foramina.

Transverse is from the Latin transversus literally meaning to turn across. It comes from the Latin trans meaning across and the verb versere meaning to turn.