What is the purpose of the 'Fillet' command in a sketch?

The 'Fillet' command in a sketch is primarily used to round off sharp corners. This is essential in design as it not only improves the aesthetic appearance of a model but can also enhance functionality by reducing stress concentrations at the corners, which can lead to cracking or failure in real-world applications.

When you apply a fillet, you select two intersecting sketch entities at their corner, and the fillet creates a smooth, curved transition between them. This is particularly important in engineering and manufacturing processes where sharp corners can be detrimental to the material strength.

In contrast, the other options serve completely different purposes; creating a hole involves subtracting material, extending lines impacts the length and junctions of sketches, and measuring distances involves evaluating dimensions within the sketch, none of which pertain to rounding corners. Hence, the fillet command is specifically designed for corner treatment, making it an essential tool in various design scenarios.