what keeps the brake pins from sliding?
 

i recently decided to have a look at my rear brakes, and aside from being disappointed with the pads the dealer installed before i bought the car, i was unable to take the bolt out of the top slider pin. since i was able to remove the bottom bolt, i just swung the caliper up, and got it off, but that put more stress on the brake hose than i am comfortable with. back to the issue, it seems like while im trying to take the bolt out, the slider spins with it. i couldnt figure out what was supposed to keep the pin from spinning with the bolt. i plan on buying a new set of pins to be on the safe side, which means i can probably just use vice grips to hold the pin steady after i take the caliper off, but im wondering if i might have issues with the caliper bracket or something