Elastic webbing - wide elastic bands are stretched across the frame and woven with wide elastic bands in the opposite direction, which are all stapled to the frame. The degree of tension of the elastic determines the firmness of the seating. The inter-woven elastic webbing provides a supportive yet flexible foundation for seating. Your weight is evenly distributed along the length of the furniture to avoid sagging or "bottoming out". This is the same suspension system used in Porsche auto-mobiles and BMW's.
Drop-in coils - Like eight way hand tied seating, drop-in coils use a coil suspension to support the seat of the furniture, like an inner spring mattress. The coil system is fit into the furniture and each coil is machine attached so that the coils do not shift out of place.
Sinuous coil or ziggersprings - this seating has the benefit of having the strength of steel and the flexible support of coil-type construction at a lesser price.