A refractory plate for a sliding gate valve at the outlet of a vessel containing molten metal has a polygonal external shape and has a longitudinal axis, on both sides of which at least two side surfaces, disposed at an obtuse angel (.gamma.) to one another, extend and serve as clamping surfaces of the plate in a metallic frame (11) or the like. The shorter side surfaces are arranged to extend at an angle (.alpha.) of between 20.degree. and 50.degree. to the longitudinal axis while the longer side surfaces are arranged to extend at an angle (.beta.) of between 10.degree. and 30.degree. to the longitudinal axis. The refractory plate can thus be optimally clamped and an increased service life is thus consequently achieved.