An important strategic weapon in seven-card stud is checking medium strength on the final river card when an opponent’s exposed cards look weak. The purpose of this check is twofold:
(1) Weak-looking cards often suggest that a straight or flush is possible, so you don’t want to be betting kings-up into a hand that will likely fold unless it beats you; and
(2) You will be giving your opponent a chance to bluff and lose more money, particularly if your hand also appears weak.
The second point is important. You should beware of weak-looking cards when bet into what look like reasonably strong hands. Most players won’t attempt to bluff with weak-appearing boards against apparent strength, because they think you will almost certainly call. But if it looks like you might also be weak or trying for a straight or flush, some opponents will try to bluff quite regularly. You should check on the river to give them this opportunity