What your talking about is part of the brake hardware that are intended to keep the pad tight and noise free. They commonly break due to wear and tear, you should always check these and replace if neccessary when you do the brake to ensure that everything works A-OK. You can usually buy the hardware kits at your local autoparts for about 10-15 bucks. One kit should do both left and right. The parts numbers for these are Front set: Raybestos H5658 Rear Set: Raybestos H5625A. Not many people bother with these details when they change their brakes, but better safe than sorry in my opinion. Don't forget to lube the guide pins (especially when changing the rears, they tend to seize up badly). Hope this helps!