A surveyor is a device used in the fabrication of removable partial dentures (RPDs) to assess and establish the path of insertion and removal. It is primarily involved in determining the guiding planes and the placement of the major connector and retentive elements like rests and minor connectors. It does not directly assess the support provided by the underlying tissues to the RPD, which is influenced by factors such as the edentulous ridge contour and the type of RPD design.