The poviting axle of the flex roller pulls seams together, while mixing the fibers for less visible seams. #'s 435, 426, and 438 have spiked wheels thar press through the pile to seal the carpet back into the hot melt adhesives. 437 bigfoor roller is made with ribbed rollers, making it especally good for fine-denier saxony, plush, and velvet carpets, as it will not snag the yarn or untwist pile fibers.