There are two different methods for making sure that your pets stay inside of the Tail Wagon. The first and easiest is to use the plastic loops which are sewn into the trailer floor/side wall for attaching a leash of your desired length. Another way to keep your pets from sneaking out the back of the trailer is to first secure the cover in place and then buckle the rear flap over the cover. Overlapping the fabric in this manner will keeps you pets more secure. This is reviewed in the owners manual as well.