What kind of temporary fencing can I use for a great dane and a bullmastiff?

As a part of my veterinary schooling, I must move to a small town for three months along with my Great Dane. I am living with another student and her bull mastiff. The back yard is only partially fenced (along the sides) not along the back or from the side of the fence to the house. We are trying to figure out a method of fencing in the back of the yard as well as the siding without actually building a fence as we are only there for three months and its a rental home. We don`t want to chain up the dogs as we don't want them to tangle and hurt them selves and possibly run away as they are strong dogs. Can any one give some possible ideas on how to keep them in and we want to take full advantage of the yard.