To address the labor market which is a priori an indefinite “thing,” firms, workers, and intermediaries require “investment in forms.” Adopting this conventionalist approach, this article analyzes the hiring channels used by firms in service-oriented sectors, asking two questions: (1) Do these channels give access to a job offer on an already-established market, or do they shape the labor supply that employers are seeking? (2) Do they convey information in standard or personalized format? The way in which the channel shapes selection depends on the ways in which the labor market is defined and the workforce described.