| 摘要 |
<p>Lag screw (1) with countersunk head (2), characterized in that between 10 and 30% of the conical surface (2a) of the head comprises slits (2b), so that with this structure and surface proportion, the lag screw of the invention allows to extract, evacuate and countersink more easily a perfect drawing, even in compact woods such as DM.</p> |
