Shielding is a Defensive Maneuver, like Charge Intercepting.

From the Saga I Rulebook:

Shield: Similar to Intercepting, a Shield allows the character to place itself in the trajectory of a Ranged Attack to protect another friendly model. That is, a character may choose to receive the impact of a ranged attack if the trajectory is within its Free Movement distance (less than 2 inches from it). Cover is not a Movement action, and a character can do it as many times as the controlling player wishes in order to protect friendly characters.