The creation of a Paris frame by Condor. The Paris features unique bi-laminations rather than lug work.
On a flat sheet of steel a design is cut. It is then manipulated by hand to join both ends together so that it resemmbles a lug. Paris bi-lams are then slotted onto the headtube.

The tubes meeting the bi-lam must perfectly meet the back of the bi-lam and sit flush. Tubing must be cut and mitred exactly to the curve of the headtube. If not the builder must begin again.

The tube must sit perfectly because any gaps will compromise the integrity of the join. Brass is then built up around the bi-lam and ajoining tube. A technique known as filet-brazing.

Link: condorcycles.com/paris