Cortosis blades were edged melee weapons that were made of, or enhanced by cortosis. Cortosis blades were made by a number of manufacturers and were widely available during the Jedi Civil War circa 3956 BBY, and were developed for a large number of reasons.
The first reason being that cortosis was capable of making many items lightsaber resistant when mixed with other ores or materials, in this way it found its way into many forms of vibroswords during the Jedi Civil War. Another use was to make pure cortosis blades, which were used to short out a lightsaber for an advantage. Many times they were capable of shorting out a lightsaber for minutes at a time, and proved to be very effective.
A type of assassin droid used by the Trade Federation during the Invasion of Naboo in 32 BBY wielded cortosis swords to duel Jedi. Obi-Wan Kenobi and Qui-Gon Jinn destroyed many of the droids.
Before and during the Clone Wars, Farghul male Harll wielded a cortosis blade, given to him by the Morgukai warriors. Jedi Master Shadday Potkin used an cortosis blade against Darth Vader during the Conclave on Kessel. Vader killed Potkin and used the blade against Jastus Farr on Kessel.