2006 Toyota Corolla Brake Pad Support Plate Shifting

Recently, I noticed a horrible grinding sound at low speeds, and now also a squeak. I discovered by pulling the LF wheel that a piece of metal called the "brake pad support plate" was making contact with the rotor (on the inside). I pushed the support plate from the outside with the tire iron until the inside and outside gaps were equal, and the noise went away. However, now it's back, how do lock this piece of metal in place to prevent it from shift?