Wearing a puṇḍra or a religious mark, especially on the forehead, is a must for every Hindu. The puṇḍra can be ūrdhva (upright or vertical) or tiryak (crosswise or horizontal). The latter is called tiryakpuṇḍra and is worn with bhasma (holy ash). (See BHASMA.)
This mark consists of three lines drawn crosswise, with bhasma, using three fingers of the right hand. These three lines are supposed to represent the three Vedas (Ṛg, Yajus and Sāma), the three syllables a, u and m of the Praṇava, the three guṇas (sattva, rajas and tamas), the three śaktis of the Divine Mother (jñānaśakti, icchāśakti, and kriyāśakti) and so on. The whole idea seems to be to bring into one’s mind, the various religio-spiritual concepts so as to feel pure and elevated.