1) If the work is not of a commercially acceptable level or quality, and/or if the contractor failed to honor the terms of the agreement or contract, you should be justified in not paying the remaining balance. Of course, your opinion is not legally binding or dispositive: if he disagrees and feels you should pay the entire amount, he could sue you (e.g. in small claims court) for the money, in which case a judge will end up deciding if you were justified in withholding the money. If you think he may sue and if you don't feel it's worth it to go to court over $250, you may wish to pay.2) If he damages the fence, you could a) press charges for vandalism or destruction of property; and/or b) sue him for the repair cost--he has no right to damage it if you don't pay, but rather should sue you if he feels you owe him money. Note however that the law will NOT presume that any damage was done by him in retaliation for nonpayment; you'd have to be able to prove he did the damage (either with witness testimony from someone who saw it, footage from a security camera, or some admission by him as to what he did or a threat as to what he would do) to take legal action.