Tsurugi's design is that of a regular katana with a red sheathe that makes it stand out. It also has three bands on the sheathe near the hand guard. The color and the bands are copied by the other 999 copies of Tsurugi.
Though treated as a single blade, Tsurugi is in fact one thousand swords with one original and 999 copies. It's strength lied in it's numbers, allowing it to be used to overwhelm the enemy.
Fitting with Shikizaki's ironic theme for his blades, Tsurugi means sword, as in a double-edged blade, while Sento means thousand sword.