Abstract: Disclosed is a sliding gate valve and clamp mechanism which permits the utilization of bandless refractory for the top plate, sliding gate, and the attachment of a replaceable collector to the sliding gate. The refractory is formed with curvilinear side edges tapered centrally toward the inter face portion between the top plate and sliding gate plate. Curvilinear edges are employed on both the stationary plate and the sliding gate, and desirably both have an identical exterior configuration, but optionally differ in the central portion where the well block nozzle is engaged by the stationary plate and where the collector is engaged by the sliding gate plate. Optionally a secondary sealing ring is employed to form a seal between the lower well nozzle and the top plate in a zero clearance environment. Also desirably the top plate and sliding gate plate may both be ground on both faces to provide parallelism and planarity of the refractory faces.