Keep them inside the house. Why would you leave toy dogs outside?
Anyway, try lining the ground around your fence with some kind of fence wall (like, lay it down) or tarp or something on the ground and nail it down with a stake or something (you can find different creative solutions at Home Depot/Lowe's). Or just leash them when they're outside.
If you really have the money and don't mind making your dogs suffering a little, they do have invisible fences which give your dogs a tiny shock if they leave a designated area. |