I check the river. I'm with you. I have no clue what he has that he could call the turn bet. But in all likelyhood, you are either crushed or he is very weak. So he's either going raise you on the river or not have much to call with anyway. Also, you're opening yourself up for a bluff river raise--even though it would seem obvious from your play that you have A-K. In NL, I'm normally checking the river in position in this situation, unless I have a REAL good read on him and this hand in particular. Or of cousre, I'm almost certain I have him crushed.