Fifth Street is the big decision point in Seven-Card Stud because that's the critical juncture in the hand when you have to put in your first big bet. While it's nice to have a made hand at this point, you don't always need one to put in a raise on Fifth Street. If you have a big draw, that can be enough to warrant raising your opponent. Some players don't think like this, and I believe that's a costly mistake.
Here's an example of a situation where I believe raising with a draw is the correct play. Let's say your opponent is showing an Ace, and you have a 7 of diamonds up and a 6 and 7 of spades in the hole, giving you a pair of 7s. You and your opponent are the only players involved in the hand, and he opens with a raise. You call.
Lesson 176: Playing Fifth Street in Seven-Card Stud (By Keith Sexton)