Which tool is most appropriate for maintaining nail length and shape?

The nail file is the most appropriate tool for maintaining nail length and shape because it is specifically designed to smooth and shape the edges of the nails. When using a nail file, you can refine the tip of the nail and achieve the desired shape, whether it be square, oval, or another style. The filing process allows for precise control over the length and contour of the nail, which is essential during nail maintenance.

Nail clippers are typically used for cutting nails, providing a more blunt edge. While clippers help in shortening nails quickly, they do not offer the finesse needed for shaping. A buffer is used primarily for adding shine to the nail surface rather than for shaping or length maintenance. A cuticle pusher is meant for managing cuticles and does not play a role in shaping the nail itself. Therefore, for tasks related to length and shape, the nail file is the optimal tool.