As Pete says, when they fail they make a terrible, pronounced rattle noise. You do not have to raise the car to check them or replace them. Reach around the front of each rear tire and you will find them.

If you have a scraping noise you probably will have to raise the rear of the car and rotate everything until you find the scraping noise. It could be wire or something dragging on the driveshaft, a rear half shaft or possibly a sheetmetal shield bent over and dragging against a rotor.

Good luck and Merry Christmas,