Heat trap on hot/cold lines?

What does a heat trap look like on a water heater? Is it something that can be replaced easily? Signs of a broken heat trap? Thanks

I know of two types, there may be more. One contains a plastic ball. They make them for both hot and cold ports on the WH, and you must get them in the right place or you'll block flow when you open a faucet.

The other type has a flap that springs back to prevent flow. Sometimes they are supplied with the WH and may incorporate a dielectric union. They often look like a galvanized nipple and may have an H or C or arrows on them to indicate the direction of flow.