What holds a CD in the jewel case?

It's the hub. Although there are a huge variety of hubs for DVD cases, the hubs for CD jewel case trays tend to look pretty similar:



Remember, CD cases are traditionally made of polystyrene, which tends to be brittle. That's why CD tray hubs are made up of tiny fingers. This provides enough flexibility for the CD to slip onto the hub, which is design to fit snugly. Notice that the hub is part of a larger area that is also raised slightly from the tray surface:

The center of the CD, which doesn't contain any recorded data, rests on the raised surface, keeping the disc surface slightly suspended – which keeps the recordable surface from getting scratched.

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