[SubaSteevo]

As Lwin said, they're little metal plates that go between the pads and the calipers. Shims are the most common (IMHO) cause of brake squealling noises, although usually the squealling would *start* when you press the brakes instead of stop (from vibrations). I was thinking that maybe they were put in incorrectly, causing them to rub until you press the brake. Then they would be pressed against the calipers evenly until you let off the brakes and they went back to their previous position. Just a thought if you've already tried braking to wear off any rust as John suggested.