There are a few spots where potential hand situations fell thru the cracks of a basic strategy chart. Here's an exerpt from the basic strategy chapter of Blackjack Bluebook II on pg 58.
DEALER'S UP-CARD
4
YOUR HAND
A/2/5
You started with a soft 13 against a 4 up. Basic strategy says to hit that, so you do and catch a 5 to give you a soft 18. Now what? Well, your chart says to double down with a soft 18 against a 4 -- but you can't double with three cards! Where the charts are concerned, that one fell through the cracks.
Most players' instincts will tell them to stand here, and that happens to be right -- in this particular case. But what if your hit card was a 4, giving you a soft 17 (A/2/4)? The right play is now to hit it! So here's the defining rule for all your multi-card soft hands;
A) Never, ever stand on any kind of soft 17.
B) Hit a multi-card soft 18 against a 9, 10 or Ace only.
And one more thing. In a few casinos, you can double down only on 9, 10 or 11. So where does that leave you if you can't double with say, A/6 against a 5? In that case;
C) Hit all your A/6's (or lower) and stand with all your A/7's or higher against a small dealer's up-card.