Abstract: The invention provides a seat comprised of spaced rectangular frame members formed of tubular plastic, the frame members being held together by at least three tubular cross members which join to the frame members by means of mechanical pressure fitting. Around the cross member is provided a webbing in a triangular-fashion. The seat has two positions, or seating modes, effected by a rotation of 90.degree..The mechanical pressure fittings comprise an expansible shaft having an outside diameter substantially the same as a tube into which it resides. The shaft is expanded by rotating a bolt which associates the shaft with an expansion wedge. The fitting further connects to a second tube transverse to the first, through the means of the same bolt and while avoiding compression of the second tube by way of an internal spacer element.