ABSTRACT
Whether an individual is allowed to enter a region, such as a room, or is excluded from it, he will often be required to show some kind of regard for the physical boundary around it, when there is one. Theoretically it is possible for boundaries like thick walls to close the region off physically from outside communication; almost always, however, some communication across the boundary is physically possible. By definition, an accessible engagement does not exhaust the situation; there is no situational closure, physical or conventional, to cut it off from nonparticipants. What we find instead is some obligation and some effort on the part of both participants and bystanders to act as if the engagement were physically cut off from the rest of the situation. Spacing will of course ensure that "talk lines" are open, that is, that persons addressing one another in an encounter will have no physical obstruction to block the free exchange of glances.
