Armless 2x4 Outdoor Sectional Piece

Assemble the seat box — two long rails, six cross members — with exterior glue and screws (pocket holes work too if you prefer hidden joinery). Square it by measuring both diagonals and adjusting until they match exactly.

Six cross members for three cushions is deliberate: a seat frame member lands under each cushion edge, so no cushion ever bridges an unsupported span.

Add the legs with the feet 28-1/2" apart — that number isn't arbitrary; it matches the companion sofa frames so the sectional's pieces sit at the same height and line. Glue and screws, two per joint minimum.

Screw the back planks to the tops of the back legs, then add the optional back support inset 1/4", screwed from the top and sides. The inset keeps the support's face behind the plane the back cushions rest on — it braces without printing a line into the cushions.

Sand, break the edges, and stain to match the rest of the sectional.

Then position it in the lineup and screw it to the adjacent sofa frames — the source calls this 'optimal support' and it's really structural necessity: armless pieces borrow their sideways stability from their neighbors. Cushions on, sectional complete, patio suddenly seats seven.