Part: Part Five - Betting Before the Flop

A cold four-bet bluff

Pre-flop
Blinds 100 / 200Pot 2,700 (13.5 BB)BBA♠5♠● 25,000 (125 BB)YOUto actUTG● 25,000 (125 BB)Openerraises 600 (3 BB)CO● 25,000 (125 BB)Aggressive 3-bettor3-bets 1,800 (9 BB)SBfoldsD

An under-the-gun player opens, an aggressive cutoff three-bets, and it folds to you in the big blind with A♠5♠.

Open, then an aggressive three-bet, and you hold A♠5♠. Best?

WhyCold four-bet as a bluff. Against an aggressive three-bettor, A-5 suited is a premium bluffing hand: it blocks his A-A and A-K, represents enormous strength, and retains a backup draw when called. Calling out of position with a weak ace is poor; the four-bet applies maximum pressure.
What happensYou cold four-bet to 4,800 (24 BB); the opener folds and the three-bettor gives up.  You take it.
An ace-blocker like A-5 suited makes an ideal cold four-bet bluff against an aggressive three-bettor - you block his strongest hands and represent the top of your range. Blockers turn weak aces into powerful bluffs.

Cold four-bet bluffs work best with ace-blockers (A-5s) against aggressive three-bettors - you block their premiums and credibly represent a monster.