Abstract: Disclosed is a process for treating a travelling film made from a molecularly-orientable synthetic thermoplastic organic polymer, according to which the film while in an unoriented condition and a molten deformable state has at least one of its sides modified so as to have a homogeneous series of high frequency discrete protuberances or depressions. This is achieved by subjecting the film to the action of an appropriately contoured surface. The frequency is at least of the order of 100 per inch. The center line average height of the protuberances or depressions is preferably from 1 to 10 microns. The process is advantageously used for making, inter alia, weaving tapes, twine and fibrous materials.Also disclosed is apparatus for carrying out such a process. In a preferred form it comprises an extruder, a pair of nip rollers, at least one of which has an appropriately contoured surface, and a hot drawing means. Also disclosed are versions including slitting means and fibrillating means.