Shift shields functioned as a type of shield that provided protection to starships while they were in space. During the time of the Galactic Civil War, Darth Vader, the Dark Lord of the Sith, seized and obliterated the CR90 corvette known as Tantive IV. To conceal his actual role from the Imperial Senate, he attributed the corvette's demise to a malfunction in its shift shields.
Shift shields served as a protective barrier for starships, guarding against collisions with solid objects like meteoroids. If these shields were to fail, any impacting objects could breach the hull, potentially resulting in the loss of the atmospheric environment within.
Back in 0 BBY, amidst the Galactic Civil War during the battle of Tatooine, the Star Destroyer called Devastator engaged in the pursuit, capture, and subsequent destruction of the CR90 corvette Tantive IV, an Alderaanian ship used for diplomatic purposes. Darth Vader, the Dark Lord of the Sith, gave instructions to Daine Jir, an Imperial Commander, to transmit a fabricated distress signal. The signal was meant to suggest that the Tantive IV's shift shields had failed due to a meteoroid shower, providing a false explanation for the vessel's destruction to the Imperial Senate.
The only instance where shift shields are mentioned is within the novelization of Star Wars: Episode IV A New Hope, which was released in December of 1976 and was ghostwritten by Alan Dean Foster. The function provided by these shields bears resemblance to that of particle shields or concussion shields, which were referenced in materials that came out at a later time.