Pieces of information and cues left by other people's actions often help us in our daily problem solving activities. In this paper, we examined the roles and functions of HARIGAMI, or stickers, from the viewpoint of social navigation. We collected 1075 pieces of HARIGAMI from 1998 to 2004. We categorized them into cognitive and social categories, and described the situations in which these HARIGAMI were used. The results indicate that HARIGAMI conveys such information as (1) traces of other people's activities, (2) most frequent uses of functions of the system on which HARIGAMI are added, and (3) environmental and system changes as time passes. By analyzing which cognitive level HARIGAMI worked on, we propose possible considerations on the refinement of the system design. HARIGAMI also works as a medium of indirect communication between users of the system on which the HARIGAMI is attached. From analysis of HARIGAMI, we need a new communication channel between users of information distributed via HARIGAMI as it can be useful to prospective users of the system.