There are various seating support options.
There is the No-Sag seating support system that is robust and versatile. It is a simple, 8-gauge sinuous spring stretched in an arch fashion and laterally mounted every 3-4 inches apart along the length of the chair or sofa. Two 8-gauge runners are mounted side-to-side, providing additional support.
The Soft Edge seating support system is very similar to No Sag with the support literally provided by the springs laterally mounted along the length of the chair or sofa and reinforced side-to-side. Soft-edge offers the added benefit of a row of vertically mounted springs that allow for flexibility along the front edge of the sofa or chair. Island Collection - St. Barts has this seating support system.
The springs are 8-way hand tied springs to ensure comfortable seating support. It is 8-gauge support coils secured and individually hand-tied eight ways to the frame itself. Each coil has an independent range of motion for maximum support. There are no pre-assembled units used and bolted into the frame as this is all labor intensive with 2-3 hours per sofa. The Bermuda Sofa and Chair uses the 8-way hand tie system.
Inside Green is the support system using Jute Webbing. This construction consists of bands of jute webbing weaved throughout the seat, back and frame.