The Lumber chair is made of thick wooden dowels and a single bent ply shell with wood upholstery.
McLellan also used the same technique to design a stool.
The following is from the Designer:
These pieces use interlocking knuckle joints similar to those found on traditional log cabins to give the frames their signature detailing, and a strength that far exceeds their visual lightness.
The beauty of the joint is that it requires very little mechanical fastening, and the connections are self tightening - any movement in the frame actually pulls the connections tighter together.
The Lumber Chair and Lumber Stool are constructed from solid ash dowels, the stool with a solid ash seat and the chair with a bent ply shell upholstered in a wool textile.