This meditation trains attention to various areas of sensation ranging from the tip of the nostrils back through the nasal passages, then the passage down to the back of the roof of the mouth, sensitized to whatever might be noticed in those areas.  Attention continues to scan forward on the roof of the mouth to the gum line and teeth, investigating sensations in those areas.  The practice continues with moving investigating attention to the lower teeth and gums, then the lower jaw.  Finally, attention is directed to include the lower and upper lip areas, with attention focused eventually on the areas just below the entries to the nostrils.  The goal of this exercise is to cultivate investigative awareness and stabilize attention away from any internal mental narratives, to increase skills necessary for vipassana, insight into the basic characteristics of self-awareness.