The issue of praying facing a sutrah in the mosque?

The Shaykh : I only intended to remind you of two matters:
The first is that when a Muslim enters the mosque, before he begins the prayer—whether it is the greeting of the mosque, the sunnah of wudu, or the sunnah of the time—he should remember that he has an obligation before he begins the prayer. This obligation is to pray facing a sutrah. For example, some of our brothers enter this place and one of them prays however it happens; this pillar serves as his sutrah, and that other pillar serves as his sutrah. Then, the brothers who are sitting, each one is facing this direction, so one who wants to pray can pray behind the sitting person, and that person becomes his sutrah.
This is the first matter I want to draw your attention to. We have reminded you of it many times, but we praise Allah (Mighty and Majestic) that in almost every lesson we see new faces who have not previously heard such a reminder and such an exhortation.