This thesis is a study of the threshold as a materialization of spatial limit; individually absolute in definition, but often part of a transition of greater scale. With the program of a public library serving as a vehicle for study, the project seeks to explore the role threshold has with the procession in architecture. This concept of spatial limit serves many roles, be it a marker of progress along the procession, a connector and separator between conflicting spatial conditions, or a manifestation of hierarchy within the building. / Master of Architecture