Thanks for the replies! That trash can lid sounds like a GREAT idea. I'll try that. There's a perfect spot on the ther side of the garage where the sun shines down REAL good. As for the "warm" thing, this isn't entirely true. If I accidentally lock a cat in the garage, I'll find paw-prints on top of anything that the cat shouldn't be on (four-wheeler, boat, tractor, etc.) The metal could be cool and they still like it. Something about the metal is attractive, maybe because it's clean (before they shed all over it). Either way, I'll try the metal trashcan lid and see what happens. As for the "smack," let me rephrase to "lightly nudged" it off the hood. (Hey at least I didn't blow it off with my new Winchester - now that would have caused great damage - JUST KIDDING!) Why spoil the fun you ask? Why don't I just go out and take my truck on the Baja 1000 and just get the damage over with, I ask. We're talkin' about a new $1500 paint job here. If they could simply hop up on the car or truck and not get muddy paw-prints, or worse, claw-marks on the paint job, I could care less. I've seen Blacky jump up, start to slip off, then kick with her back-legs making a noise similar to draggin your nails down a chalk-board. That's FAR worse than the noise emitted by the Cat-Whistle. TRUST ME. I don't want to do anything to hurt my kitties, but I look at the ultra-sonic whistle like the underground electric perimeters people use to keep their dogs in with: It only takes one or two "corrections" and they learn to stay away from the boundaries. However, I'll try the trash-can lid first, and if that works, no ultra-sonic whistle. Thanks again folks!