| 摘要 |
<p>A screw driver has a handle, shaft and blade with the bottom edge of the blade being flat and having flat sides which include inwardly from the bottom edge. To turn the screw, the screw driver is placed with its bottom edge in the gap between protruding (raised) quadrant sectors of the screw head and turned 45.degree.. The flat inwardly inclined sides of the screw driver act against cut-back flat sides of the protruding sectors to cam the screw driver toward the screw head and rotate the screw.</p> |
