| 摘要 |
A wrench comprises a rod, a retainer, and a casing for accommodating the retainer and allowing relative rotational movement between the casing and the retainer. The rod comprises a driving portion on an end thereof for engaging with a fastener. The retainer has a central portion securely mounted to the rod to turn therewith. At least one engaging member is mounted in the casing and biased to selectively engage with one of plural retaining sections of the retainer, thereby exerting an engaging force between the engaging member and an associated retaining section of the retainer. When a rotational force applied to the casing is smaller than the engaging force, the retainer and the rod are turned to thereby turn the fastener. When the rotational force applied to the casing is greater than the engaging force, the casing slides while the retainer and the rod are not turned.
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