The steamed knee that eliminated the apron frame
Conventional wooden chairs require a perimeter rail (apron) underneath the seat to prevent the legs from splaying outward under load. That rail consumes knee clearance and adds four mortise-and-tenon joints that loosen in dry winter heating. Collaborating with master cabinetmaker Otto Korhonen in Turku, Alvar Aalto cut parallel saw kerfs into the end of a solid birch billet, inserted thin veneers coated in casein glue, and bent the timber 90 degrees in a heated press.
Because the horizontal foot of the "L" screws directly into the underside of the circular seat, the leg becomes a self-bracing bracket. The same L-leg scales up in thickness to support child stools, six-person dining tables, and library desks, creating a unified structural vocabulary across an entire apartment.