Sakura catches the Sword card in the second volume of the manga. Sakura and her friends went Christmas shopping together. They found a nice store that had cute pins, and both Sakura and Rika bought one. The one Rika bought was a small sword. Everyone was pleased with their purchases and they went home.
Sakura was talking with Kero-chan when her doorbell rings. When she answers it, it is Rika! Only, she is acting strangely, and attacks Sakura with a sword! Obviously this was the work of a Clow Card! Kero-chan told Sakura that she had to get Rika to drop the sword, but Rika was attacking and Sakura didn't want to hurt her! Rika would have cut Sakura if Syaoran hadn't blocked her! Sakura used the Illusion card to distract Rika while she slapped the sword from her hand.
The Sword card is primarily an offensive card, and is very powerful. It is very useful in catching other cards!