Think about the back of sit-com couches or the couch in your grandma's house. What is almost always folded neatly on the sofa back, or stacked in linen closets and hope chests? A granny square afghan.

Knitting a spare-yarn afghan is a quick and easy way to save money. There seems to be a law-probably written by a close relative of Murphy ­dictating that needlecrafters will never have just the right ...