Which type of wrench is the best choice for a large square nut?

The monkey wrench is the best choice for a large square nut due to its adjustable jaw mechanism, which allows it to grip a variety of nut sizes securely. The design of this tool provides a strong grip and the ability to apply significant torque, making it useful for both tightening and loosening large components. The movable jaw accommodates different widths, making it versatile for various sizes of square nuts typically found in plumbing and other applications where large fasteners are used.

In this scenario, while other wrenches may be capable of handling fasteners, they might not provide the same versatility or grip strength as the monkey wrench. For example, a spanner is often more suited for fixed-sized nuts and bolts rather than adjustable grips, while a Stillson wrench is primarily designed for plumbing applications with round pipes rather than square nuts. The Spintite wrench, although useful in specific situations, is less commonly applied to square nuts compared to the monkey wrench. Thus, the monkey wrench stands out as the most effective option for this particular task.