Abstract: Concrete septic tanks have inflow and outflow orifices and near the outflow orifice have screening or baffles which are stapled or bolted to the concrete inner wall so as to force the outflowing liquids to pass a predetermined flow path with the hope to avoid solids passing out of the tank and into a draining tile bed. A novel baffle structure and device for attaching the baffles is disclosed using a linear race with forward and rearward recesses and flexible marginal flap that seals the race onto a core surface of a mold use to fabricate the tank. After the concrete is poured into the mold and partially cured the core is then removed, and the track remains embedded in the concrete and acts as a holding, sealing and anchoring for a baffle, preferably made of a non-corrosive material such as a plastic. The baffle is slipped into the race of the track and seepage across the baffle interface with the tank walls is avoided and the predetermined flow path for the outflowing fluids is ensured.