Wrench capable of preventing a screwed member from slipping out and holding the screwed member

Wrench capable of preventing a screwed member from slipping out and holding the screwed member, the wrench comprising at least one box end, a head section of the box end being formed with a polygonal socket having multiple teeth on inner circumference for engaging with a polygonal screwed member, said wrench further comprising:

• an annular groove formed in the head section;
• and
• a retainer ring disposed in the annular groove, the retainer ring being resiliently stretchable, an inner edge of the retainer ring protruding into the socket, whereby in normal state, a gap exists between the retainer ring and inner circumference of the annular groove, permitting the retainer ring to resiliently stretch outward, the retainer ring forming a stopper section in the head section, whereby when the socket is fitted onto a screwed member, the retainer ring serves to stop the screwed member from slipping out of the socket and the retainer ring is resiliently stretched to make the screwed member fitted into the retainer ring and held thereby.