The fat separator makes gravies and sauces nearly fat free with little effort. When pan drippings are poured into the separator the fat will rise to the top and the juices will settle to the bottom. Because the spout originates at the bottom, below the level of the fat, you can pour the juices off separately and leave the fat behind.
This one is made of tempered gless, and relatively expensive, but you can find fat seperators in kitchen departments for $10.00 and up. I think they are well worth the investment.