[asid61]

I've had to learn to tram the head and such. A few good ways to demonstrate the importance come to mind:
1. Hole sizes. A hole that is 0.001" oversize is vastly difference than 0.001" undersized for bearings and such
2. Squareness. Even a 0.002" off-square block can be seen with a trued square.
3. Gear spacing (?). It's possible to demonstrate it this way.
4. Hole spacing, for dowel pins.