US Patent 7194935 Hexagonal driving tool with pawl piece

A hexagonal driving tool includes a socket having a reception hole and the socket is connected with a hand tool. A hexagonal driving rod has a first end inserted in the reception hole and a groove is defined longitudinally in the hexagonal driving rod. A recess is defined transversely in the hexagonal driving rod and communicates with the groove. An elongate pawl piece is received in the groove and a first spring is located between the pawl piece and an inner surface of the recess. The first spring pushes one of two sides of the pawl piece out from the groove so as to be engaged with a rounded corner of a rounded hexagonal recess in the head of a bolt or screw.