Abstract: There is disclosed a traveling grate apparatus wherein materials are treated at an elevated temperature for purposes such as sintering, pelletizing, calcining, and the like. In such apparatus, a grate and upstanding side plates form a channel for carrying the material along. Each side plate has along its inner face a bench for holding the material to be treated. As the treatment of material effects changes in the volume of the material, the material tends to lose contact with the side wall, but, by resting on the bench, a seal is provided to prevent direct passage of gases through the bed in the sidewall sections.