a method and an apparatus for making an endless , flat , flexible belt of pourable plastics include a core , especially a multiple core , as tension bearer , for example in a conveyor belt of polyurethane . spaced apart support filaments extending transversely of the longitudinal direction of the belt are tightened in a mold approximately in the center plane of the belt to be cast so that the tension bearer will be placed as accurately as possible in the middle , based on the thickness of the belt to be produced . subsequently the tension bearer is wound in longitudinal direction of the belt on the winding support formed by the support filaments . thereupon liquid plastic material is poured into the mold and following that the support filaments protruding from the side surfaces of the belt are cut off upon termination of the curing .