| 摘要 |
<p>A screw (1) includes a screw shaft (2) that has a pointed boring portion (3) on a front end thereof and has, on a rear end thereof, a head (4) with a torque transmitting hole (5). A large-diameter washer (10) is assembled, in a detent manner, to a base of the screw shaft (2) just below the head (4). The large-diameter washer (10) is provided with a pair of cutting blades (14) at respective positions that are opposite each other in a diameter direction of the large-diameter washer (10) and that are symmetrical to each other with respect to the screw shaft (2). At an initial stage of screw fastening, respective outer end edges of the pair of cutting blades (14) act as cutting blade edges (14a) to cut into a rubber sheet (23) that forms a surface layer, and then the pair of cutting blades (14) cuts through the rubber sheet (23) and enters under the rubber sheet (23). Thus, the screw shaft (2) goes straight ahead without inclination and reaches a thin steel plate (21) that forms a lower layer of a roof member (20) or an exterior wall member both having a three-layer structure such that the thin steel plate (21) is fixed to a support member (27).</p> |
