Tolerance stack-up refers to the cumulative effect of individual part tolerances in an assembly. When multiple parts are assembled, each part has a specified tolerance, which is the allowable variation in its dimensions. These variations can add up, potentially leading to misalignment or functional issues in the final product. To analyze tolerance stack-up, engineers often use methods like worst-case analysis or statistical analysis. This helps ensure that the assembled product meets design specifications and functions correctly, even when parts are at their extreme tolerance limits. Proper management of tolerance stack-up is crucial in fields like manufacturing and engineering.