Constraints in user interfaces serve as effective tools to prevent slips by ensuring users can only make choices that are valid and intended. This helps prevent errors and enhances usability by simplifying decision-making processes. For example, when filling out an online form to schedule an appointment, the interface might constrain input by allowing users to select times only within business hours. This prevents the common slip of scheduling a meeting at an unavailable time. The system could automatically gray out or remove times outside of business hours, ensuring users only choose from viable options.

Constraints guide users smoothly through tasks, preventing mistakes and making interactions more straightforward and error-free.