The invention relates to a method of manufacturing a fiber mat adapted for use in the manufacture of a fiber-reinforced device, said fiber mat comprising at least two essentially longitudinally extending and parallel batches of fibers. Novel aspects of the method according to the invention involves that the method comprises that the batches are joined by holder means that span above or below each batch, whereby the holder means impart an influence to each batch which is essentially symmetrical about an axis situated longitudinally between the batches. A symmetrical influence about an axis longitudinally between the batches accomplishes that influence from one side is matched by influence from an opposite side. Hereby it is prevented that the batch will undulate. Simultaneously the batches are clearly separated, whereby resin is more easily conducted longitudinally of the batches.