I agree with slicendice, but i would dig my hole about 2 ft deep and at a 45 degree angle, then i would put fox bait on a back stop such as a stump (dig the hole close to the backstop) then bed the trap so it is solid and doesnt move under any pressure, if fox feel this they will flip over ur trap and u will never catch one. Another trick that works good is that if u have some white deer hide or sheep wool stick a piece of that down it the hole to make it look like a mouse and keep their attention. Another alternative for the toilet paper is a piece of screen the size of the jaws. Another trick is to have your trap pan in the lowest spot. this is where predators will step. You can also place sticks around the trap to make sure they come form the front instead of the side or back, cuz predators will not step on sticks when the are sneaking up on prey. Then when u get your set how u like it i would brush away all the tracks and spray everywhere you have stepped or touched with fox urine. Use a pair to set the trap (new gloves) and any pair you want to scent and spray urine with.

GOOD LUCK!!!