An oven is provided including a cooking cavity having side walls each including a protruding divider rail extending horizontally along the side wall and a divider rail emboss disposed above the protruding divider rail; and a divider assembly to divide the cooking cavity into cooking subcavities. The divider assembly includes: a panel having a bottom surface, and first and second side edges, the first and second side edges each having a recess; movable closures positioned within the recesses; a plurality of springs positioned within the recesses for biasing the movable closures out from the recesses while allowing the movable closures to slide inward inside the recesses, wherein the movable closures are configured to extend into the respective divider rail embosses when the bottom surface of the panel rests on the protruding divider rails so as to lock the divider assembly in place while increasing airtightness and reducing heat migration.