US Patent 6951158 System comprising a screw and a tool therefor

System comprising a crew and a tool (6) therefore, in which the screw head (1) with a slot (2), the slot (2) having a first recess (3) with an approximately straight-walled cross section, and the tool being provided with an engagement section (16) that is complementary to the first recess (3). The slot has a second recess (11) at the bottom of the first recess (3), with a smaller diameter than that of the recess (3), and the tool (6) is provided with a central point (17) that complements the second recess (11). The second recess (11) has a circular cross section and the central point (17) has a circular cross section.