Which tool is appropriate for cutting a 1" x 4" plank down to 3 inches?

The ripsaw is specifically designed to cut along the grain of the wood, making it suitable for cutting a plank down to a specific width. In this case, the task is to reduce the width of a 1" x 4" plank to 3 inches. The ripsaw's design allows it to efficiently saw through the fibers of the wood without causing tear-out along the edges, which is crucial when you need a clean, straight cut.

While other tools like the handsaw and jigsaw can also make the cut, they may not be as efficient or ideal for this particular task compared to a ripsaw. A handsaw can be used for various cuts but isn't specialized for ripping cuts along the grain. A jigsaw is more versatile for intricate cuts but is generally not recommended for long straight cuts in thicker wood, as it can lead to less precision. The coping saw is specifically used for making intricate cuts and curves, which is not necessary here.

Therefore, the ripsaw stands out as the best choice for performing a clean and precise cut on a plank in this context.