Traditionally the best frames have been made of kiln-dried hardwood which resists warping. Today, quality frames may also be made of steel, plastic, laminated boards or a combination of materials. Support can be provided by webbing, sling straps, slats or springs of various types. The design, size and amount of support or softness desired by the designer will determine which type the designer uses. In this method each coil spring is placed in the seat by hand and a skilled craftsman ties the coil into place with twine and interlocks it with other coils using an intricate set of knots.
Coil springs add depth and comfort but require adequate space.
There are many comfortable, sleek, slim styles using the S-type spring. It's another example of how modern technology makes it possible to have good looking, comfortable, serviceable upholstered furniture at imminently affordable prices. Cushioning forms the next layer in the comfort story. Cushioning materials include cotton or polyester, polyurethane foam and, of course, down. Foam and polyester fiberfill wrap are much-used padding materials.