You can use this feature to identify which of the built-in parts have changed over the years (if you have the same product displaying a different parts list). The parts lists differ depending on year of manufacture. If you are unsure of the date of manufacture of the defective product you can check in Model History whether the replacement part can be found in all models or whether it was substituted by another part over the years. If you cannot see the part in Model History you can use any of the diagrams for parts identification purposes.