I understand your predicament well! I have 2 escape artists myself and I've tried everything!! cement blocks all along the bottom of the fence, laying cement into the ground, all sorts of stuff. Couple of options, if the fence is chainlink, it's a good idea to sink it 6 or so inches into the ground. Another alternative is to buy extra fencing (something durable!) and put it around the bottom of the fence, possibly sinking it into the ground. Since they're fairly little, big, heavy duty cement blocks might do the trick. I'll have to agree with the consensus on tie-outs. Extremely dangerous, even illegal in some states. Good luck and I hope it works out!

~JC