I have a '02 F150FX4, having trouble getting my back tires off...is there some sort of lock on them?

(If aluminum wheels) chances are that wheels have "corroded" to brake rotor hub. Jack up vehicle SECURELY so there's no chance of it falling off the jackstands, loosen the lug nuts a few turns each, then you have to literally kick the wheels outward from under the vehicle. If you feel that's too risky, use a rubber mallet to bang against the inside of the tire while the vehicle is securely jacked up (after loosening the lug nuts).

I'd think it would be safer if he'd just work it side to side from the outside of the vehicle. Just kick the front of the tire then the back until your able to get it off. PLEASE BE CAREFUL safety first.

Before you put the tires back on rub some oil (very little) on the inside face of the rim that touches the drum and you'll never have that problem again as long as you do it periodically. And I would sand or steel wool some of the corrosion off before the oil treatment. If you have owned it since '02 how many times before have you rotated the tires. if you rotate them every 5,000 - 7,500 miles you should not have that problem.

I use a little anti-sieze on mine,I try to keep it on hand for various other things besides the toyz.

all sounds like good advise.