There are two ways to tell if the timing belt has been replaced. One is obvious-you are looking at a service receipt showing the replacement.
Swimlane diagrams are used whenever you need to show activities, tasks, or process steps which are being performed by different actors/roles. You can use swimlanes to group activities in an activity diagram or process flow by any category what you need: by role, by system, by department, etc.
Bearing spacers. Bearing spacers are small metal cylinders that fit into a skateboard wheel between the bearings. Their purpose is to reduce the weight distributed to each bearing, which can make your turns smoother and more stable and also extend the life of your bearings.