Brakes problem
2004 Ford Expedition V6 Two Wheel Drive Automatic 53,245 miles

I am replacing the front brake pads, I am having trouble removing the caliper mounting bolts, am I supposed to use a wrench or a Allen wrench? I tried a socket wrench, but could not find the correct size, i notice what seems to be a allen wrench hole in the middle of bolt head, but tried several sizes of allen wrench... Thanks for any assitance