A blocking member for use in a vent bore in a mold for the manufacture of technical rubber products, in particular to the manufacture of vehicle tires, wherein each blocking member has a tubular hollow body which can be fixed in force-transmitting manner in the respective bore, the hollow body having a sealing part formed thereon in one piece with it. The sealing part has a plate element disposed at the inner side of the mold which is provided in its plate surface with at least one slot opening and the peripheral rim of the plate element projects at least regionally beyond the bore diameter of the associated vent bore and contacts the inner side of the mold.