Conducted 2 studies with 289 graduate and undergraduate students to learn about the meaning and function of spatial markers and their relation to personal distance, territorial, and jurisdictional concepts. Using field methods, Exp. I found that the choice of seating and the duration one remained at a table in the library were affected by the presence of people more than by the presence of a marker. Markers function to protect the space around them by eliciting reactions to decreased personal distance, not by signifying that the area is occupied. Using stimulus photographs and questionnaire responses, Exp. II found that no S would sit at a marked location, and that Ss expressed the desire to avoid a confrontation with an intruder or owner of a marker. Markers reduce or eliminate conflict over space by creating an effective warning device system. The jurisdictional concept is proposed as more appropriate than the territorial concept to describe spatial ownership in public areas. (20 ref.) (PsycINFO Database Record (c) 2016 APA, all rights reserved)