in a conventional manner rotatably mounted on the axle bolt 44 is a center roller 48 a first end roller 50 and a second end roller 52 each of which are provided with apertures 54 56 and 58 the aperture 56 that is provided on the center roller 48 is larger in diameter than the diameter of the axle bolt 44 so that the center roller 48 may rise up over caps or plates 60 that are fastened to the roof 62 by nails 66 and a layer of overlapping membrane 66 apertures 54 and 56 have the same diameter and freely rotate on axle bolt 44 preferably all the rollers 48 50 and 52 are sufficiently weighted to apply pressure to the overlapping membrane 72 with the first end roller 50 being of a different length than the second end roller 52 both of which are shorter in length than the center roller 48 the center roller 48 being the longest roller is shown in its raised position by the broken line 68 in fig1 the center roller 48 may also be provided with a thick coating of resilient material 70 if desired to provide additional pressure to seal around the caps or plates 60 the rollers 48 50 and 52 are readily changeable to work on different size caps and plates 60 2 or 3 inches round or square or be changed in size to work on heat welding machines not shown for single ply roofing membranes 66 preferably the rollers 48 50 and 52 are fabricated from cold rolled steel having a diameter of 21 2 inches the first end roller 50 is 11 2 inches long the second end roller 52 is 1 inch long and the center roller is 31 2 inches.