Abstract: A hexagonal wrench has a head. The head has an end surface, six equal side surfaces and at least one groove. Each side surface has a left edge segment and a right edge segment adjacent to the left edge segment of an adjacent side surface. The at least one groove is formed in at least one of the right edge segments and the left edge segments and extends to the end surface. Therefore, the head can engage securely an inner surface of a socket to rotate the socket even when the socket is worn or rounded.

Abstract: A telescopic device with a firm positioning effect, comprises a hollow upper sleeve having at least one arcuate recess at the inner wall thereof, and having a through hole at the top portion thereof and internal threads at the lower end thereof; a hollow lower sleeve having external threads disposed at the upper end thereof to be threadedly connected to the internal threads of the hollow upper sleeve, and a hole formed on the lower end thereof; a guide mechanism disposed at the internal portion of the hollow upper sleeve and hollow lower sleeve, and including an intermediate body having a ring portion at top end thereof, a thin rod disposed on the ring portion and a thick rod disposed at the lower end of the intermediate body wherein the thin rod extends to protrude the outside of the top portion of the hollow upper sleeve while the lower end of the thick rod may protrude from the hole of the hollow lower sleeve; a spring positioned at the internal portion of the hollow lower sleeve and through which the thic