This article explains how to use an ‘extension’ for the purpose of convenience (perhaps a hex or 12 point socket or an allen wrench or other tool won’t fit at the end of a torque wrench where you need it); or, perhaps you want to increase the range of a torque wrench.

This article explains how to use an extension for such as the Airheads U-joint flange bolts, where you simply cannot get a torque wrench without an extension to fit properly, due to the limited room between the bolt and the U-joint body.

Another usage might be that if you only have a 75 ftlb maximum indication torque wrench and need to tighten the wheel bolts on your Paralever bike to 105 ftlbs,  ….you can do it with an extension, and this article explains it.