The top of the springs have a lot more movement than the bottom. The bottoms can be attached using hog rings, they are much faster than sewing and less expensive than a clintch it tool, but work well. It is important to get the bottom of the springs attached in the proper spot. Hand tying really is not that bad once you get the hang of it and a sofa can be sprung up within three or four hours. A drop in spring unit can be used, its called a Webline. Uses coil springs within a metal frame that can be installed into the chair or sofa, but imo they are a poor substitute for traditional hand tied coil springs.