Abstract: A first wrench adapted at one or both ends to receive an end of a second wrench to permit use of the second wrench as a lever arm extension to the first wrench. The invention provides a reliable coupling of the two wrenches. The first wrench may be a box or a combination wrench. An open-end portion of a second wrench is interlocked through a box-end of the first wrench. A slot structure on the first wrench can transform a torque from the second wrench to an augmenting force to increase a torque applied by the first wrench on a bolt or nut. The slot may be complimented by a notch located diametrically opposite, and on an opposite side of the box-end, from the slot. If present, a notch receives handle structure of the second wrench.