This plate has locking tabs to hold the 45 DCOE Venturi Retaining Screw (Part No. WC-64840.003, sold separately) in place on the underside of the 45 DCOE carburetor. This plate should be replaced whenever the venturi screw is removed to ensure proper locking. 2 required per carburetor; sold individually. Not used on the 40 DCOE.