What is the name for a non-adjustable wrench with accurately machined openings on either end?

A non-adjustable wrench with accurately machined openings on either end is known as a box wrench. This tool features one or more closed ends that fit snugly over a nut or bolt, providing excellent grip and minimizing the risk of rounding off the corners, which is especially important in applications where high torque is necessary. The precise machining ensures that the fit is tight and secure, allowing for effective turning of fasteners.

On the other hand, an open end wrench has a U-shaped design that grips the sides of a nut or bolt but lacks a completely closed end like a box wrench. A tire wrench, while also a type of non-adjustable wrench, is specifically designed for removing or tightening lug nuts on vehicle wheels, which may not necessarily have the dual ends characteristic of a box wrench. The answer effectively highlights the specific design and functionality that defines a box wrench in carpentry and building construction contexts.