a composite box end wrench has a non - metallic body including a handle portion and at least one head portion which defines a fastener - receiving opening therethrough . the wrench includes strengthening and / or retaining structure which strengthens the head portion and can change the failure mode to confine wrench parts in the event of failure . in one embodiment each head portion has a fastener - engaging member insert molded therein along with a reinforcing plate which encircles the member and preferably extends slightly into the handle portion . the reinforcing structure could alternatively be a band extending the length of the wrench and encircling the fastener - engaging member . in a ratcheting version of the wrench the non - metallic body may be split lengthwise into two parts , each of which has reinforcing structure embedded therein , the fastener - engaging member being a ratchet gear which , along with an associated pawl , is disposed between the body parts . the parts may either confine or expose a peripheral portion of the gear , and the reinforcing structure encircles hub portions of the pawl and gear to the hold them together . the body parts may be secured together by various means , including pinning , ultrasonic welding and snap - fitting . the wrench body may be provided with an outer non - metallic sheath , in addition to or in lieu of the reinforcing structure , which sheath covers at least the handle portion of the body .