A catheter has a deflection beam and a single continuous puller wire to effectuate bi-directional deflection. A joint between a catheter body and a deflectable distal section effectively transmits torque from a control handle. The joint includes two open-shaped brackets, each affixed to a respective side of the flat deflection beam to form a closed-shaped hollow body that bridges and circumferentially encircles the beam. Each bracket has through-holes into which thermoplastic material of the catheter body and the deflectable distal section can melt and migrate to form interlocking nodes.