YES, congratulations on your rescues !!!
But PLEASE forget about that type of confinement for your guys. It's cruel and it could effect their health as has been stated !
There are other options. Until you could put up a permanent perimeter fence, you could do a temporary. A few metal Stakes and a Roll of wire fencing would provide you with an enclosure you could supervise them in, and still let them run free (to a point). You also could do a "Run", which is a rope tied between two points and a Leash for them, looks like this...
http://www.yorkietalk.com/forums/pic...ctureid=122721