What kind of transmission line has two conductors maintained side by side, a constant distance apart, using insulated spreaders?

Open-wire line, also known as ladder line, consists of two parallel conductors held at a constant distance from each other using periodic insulating spacers called spreaders. This construction primarily uses air as the dielectric, which results in extremely low signal loss. While twin-lead is also a parallel-conductor line, it is manufactured with a continuous ribbon of solid plastic insulation between the wires rather than separate spreaders. Twisted pair consists of intertwined wires with no fixed spacing, and coaxial cable features a central conductor surrounded by a tubular shield. Because the question specifically mentions 'insulated spreaders' maintaining a constant distance side by side, it accurately describes traditional open-wire line.