In normal natural dentition, there exists an anteroposterior curve that passes through the cusp tip of the mandibular canine and the buccal cusp tip of the mandibular premolars and molars, and that extends in a posterior direction to pass through the most anterior point of the mandibular condyle, originally described by Ferdinand Graf Spee in 1890.
Restoration of the dentition to such an altered occlusal plane can introduce posterior protrusive interferences.
The broadricks flag permits construction of the curve of spee in harmony with anterior condylar guidance allowing total posterior tooth disocclusion on mandibular protrusion.
Unfortunately, the devices can be confusing to assemble because each device consists of three pieces that can be assembled in multiple ways, and there are three types of such devices for anterior, posterior and bitewing radiographs (in addition to a fourth accessory device for taking endodontic radiographs).
The film-holding plane of the posterior film holder is wider than the plane that has the metal prong insertion holes.
The bitewing metal rod is straight with no bends, while the posterior metal rod has one 90 degree bend.