A method for forming seals on vehicle bodies produces by extrusion a sealing material strand to be processed to form a multiplicity of seals, coils the sealing material strand to form a transportable unit, transports the transportable unit to a processing site, and supplies the sealing material strand continuously at the processing site using the transportable unit to a processing device which forms the seals, wherein, within the scope of the processing, a portion of the sealing material strand to be applied to the relevant seal support seat and forming the seal is severed from the sealing material strand in each case. Within the scope of producing the sealing material strand, the sealing material strand portions which in each case form a seal are produced with a cross section changing in the longitudinal direction of the strand, and, within the scope of processing the sealing material strand, separating points which are required for severing the sealing material strand portions which in each case form a seal are determined by detecting markings which are produced on the sealing material strand before the transportable unit is formed and/or by detecting changes in the cross section of the sealing material strand that occur at certain longitudinal positions of the sealing material strand portions.