We were camping next to an Airstream this weekend which had some cone shaped blocks under the stabalizer jacks. I asked the owner about them and he said they are designed to raise beds so you can store stuff under them. He said they are great for off level sites or just so you don't have to drop the jacks as far. We ended up having a very nice conversation and when we broke camp this morning he came over and gave them to me!
Nice to know there are still good people in this world. Here's a picture of them, they are very lightweight and you can stack them so they don't take up much room.