I got mine at a local pet store but here it is on eBay for-well I'm somewhat irritated for how much I paid for it now LOL! I had the pink camo one-it was great! You use the harness as any harness and then belt attachment clips onto the D-ring just as a leash would and the other end of the attachment clips into the belt buckle just as a seat belt would. Amazed at how stinking cheap it on on eBay! Here's the link!
Dog Car Safety Restraint Seat Belt Harness 7-15" Chest - eBay (item 350373860862 end time Dec-10-10 18:01:03 PST) I've heard great things about the ones that the seat belt goes through but the belts don't always go into restrain lock when you just stop short-and your dog still may be rolled and won't be restrained-or when you dog is just trying to run around the car-I know this one lists it only works on certain models but I've used mine in multiple vehicles and haven't had it not work yet-could look into the one's that clip to the car seat upper restraint-if you have one installed in your car.