What is the function of a 'lock' in a sketch?

In a sketch, the function of a 'lock' is to restrain size and angle. When a sketch entity, such as a line or a circle, is locked, it is essentially constrained, meaning its dimensions and angular relationships cannot be altered unintentionally. This locking mechanism ensures that certain parts of the sketch maintain specific relationships and dimensions relative to one another, which is crucial for preserving design intent as modifications are made to the sketch.

By applying a lock constraint, designers can set critical dimensions or angles that should remain constant throughout the design process, even when other parts of the sketch are manipulated. This helps maintain the integrity of the geometry, ensuring that it behaves predictably as further design changes occur.

This is particularly useful in complex sketches where keeping certain elements fixed is necessary for continuity in the overall design. In effect, locking adds an additional layer of control, which can help prevent problems that may arise from accidental alterations to crucial dimensions or angles within the sketch.