Tube sock w/knots... that is what I have been doing with my pup (she is a non-Rott, leave it at that! :p )
oh, and we also play tug with all towels, rugs, robes, anything that dangles in front of her!! :D
she especially loves the bath mat in my bathroom!!! everytime she sees the door is cracked.... there she goes with it!!
sucks getting outta the shower, to step on cold wet tile
