rear rotor bolts

[Honda4life05]

i own a honda 300ex an i was changing out the back rotor an when i was taking one of the four bolts off all it did was spin..the other side of the bolt is round an i cant get a grip on it with anythig..are there grooves on the bolt that keep it from spinning? if so can i put anything on the bolt to kepp it from spinnig?


thanks.