The paired lightsabers of Asajj Ventress.
Interlocking hilts, also known by other names such as paired lightsabers, locking lightsabers, or even form shifting lightsabers, refer to a set of two lightsabers designed to be combined at the hilt. This connection could be achieved through a locking mechanism, effectively creating a double-bladed lightsaber, or by using a fiber cord, allowing the lightsabers to be wielded in a flail-like manner.
One of the initial individuals to utilize paired lightsabers was Kas'im, a Sith Blademaster. He employed the pairing feature to conceal his two lightsabers as a single saberstaff before separating them into individual weapons. He strategically used this technique with considerable success against Darth Bane on the planet Lehon.
Komari Vosa was also known for wielding paired lightsabers. Following Vosa's demise, her lightsabers were presented to Asajj Ventress by her former master, Dooku. These weapons possessed both connection methods: the locking mechanism and the fiber cord. Ventress frequently used the locking mechanism, wielding the weapons as a double-bladed lightsaber. Although she typically preferred the locking mechanism, using the fiber cord connection resulted in a weapon that was harder to manage compared to a standard double-bladed lightsaber. However, the curved hilts and the fiber cord joint provided the advantage of striking from unexpected directions. Ventress demonstrated significant skill with these weapons, but it wasn't sufficient to overcome experienced Jedi Masters like Mace Windu or Obi-Wan Kenobi.
Sa Cuis, an Emperor's Hand, was among the later users of paired lightsabers. However, it seems Cuis primarily used the pairing capability for convenient storage, preferring to wield his lightsabers separately during combat.