So I've got a little five month old chihuahua mix that I'm trying to train as per the training guide that's on the website. I'm currently trying to get him to learn the down command (he's got the sit command down), but I've run into a little snag. We have an all-tile house, and while he'll sit on the tile, he refuses to lay down on it. He'll follow a treat down to the ground when he's on a rug or blanket, but I can't get him to do it on tile. How can I get him to do this on tile, or will he lay down anywhere once he's mastered the command?