The old rocking chair...

One day a man came home and found his grandfather sat on his rocking chair in the veranda - naked from the waist down. Rather perplexed, he asked the old man, "Why are you sitting there naked from the waist down? You'll catch your death of cold." So his grandfather explained, "Well, yesterday I sat here naked from the waist up and got a stiff neck... This is your grandmother's idea."