We lamb outside now, but years ago we lambed our Jacobs inside. OH knocked up some hurdles from wood which worked very well and were cheaper than buying. If you have your ewes lambing in one area, you run the risk of lamb theft. It does sometimes happen even when lambing outdoors if a ewe in labour is close to one which has just delivered, she will assume that the new lamb is hers. If you have only 4 ewes, presumably they will not all be lambing on the same day so you only need one or two pens.