Abstract: A letter sorting system includes a row of juxtaposed stack compartments; a material intake device arranged along and spaced from the compartments; a carriage arranged for travel along the compartments; and a transfer bridge mounted on the carriage to be displaced thereby along the compartments. The transfer bridge includes an exterior frame pivotally attached to the carriage for pivotal motions into first and second positions; an interior frame pivotally attached to the exterior frame for pivotal motions into first and second positions; and a slide having a first part attached to the interior frame and a second part attached to the exterior frame. Dependent upon simultaneous positions of the exterior and interior frames, the transfer bridge may assume first, second and third operating positions.