Gather the correct tubing, flare nut, double-flaring tool, tubing cutter, deburring tool, and vise
Slide the flare nut onto the brake line before making the flare
Cut the brake line square with a tubing cutter
Deburr the inside and outside edges of the cut end
Clamp the line in the flaring tool at the correct height for the flare type
Form the first flare with the tool
Fold the first flare back to create the final double flare if required
Inspect the flare for even shape, cracks, and smooth edges
Test-fit the flare nut and mating fitting
Repeat the process if the flare is uneven or damaged
Tighten the fitting to the specified torque after installation