This chapter examines the concept of a tourist attraction system consisting of three elements: the attraction or nucleus itself, the tourist, and the marker or gatekeeper that connects the tourist to the attraction. In many ways, markers and gatekeepers are the most important part of the system, for they help shape the expected experience, convey desirable or undesirable messages to the tourist and provide information that acts as a catalyst to visit. A range of markers is discussed. The chapter then focuses on the role of gatekeepers as knowledge brokers who may intentionally or unintentionally inform initial expectations of a place being visited, shape the message selectively to suit various political goals or act as mediators that can provide or limit access to information. It then discusses how the number of gatekeepers and their proximity to either the consumer or the product influences experiences. The chapter then discusses a range of gatekeepers including on-site guides, social media, staff at tourist information centers and members of the travel trade.