Part: Part Five - Betting Before the Flop

A light three-bet

Pre-flop
Blinds 100 / 200Pot 900 (4.5 BB)BBA♦5♦● 25,000 (125 BB)YOUto actBTN● 25,000 (125 BB)Wide buttonraises 500 (2.5 BB)SBfoldsD

A loose button that steals constantly opens to 500. You're in the big blind with A♦5♦.

A wide-stealing button opens to 500 (2.5 BB); you hold A♦5♦ in the BB. Best?

WhyA button opening far too wide is folding out a big chunk of his range to a reraise, and A-5 suited is the tool: the ace blocks the strong aces he'd continue with, and when he calls you still flop flushes, straights, and pairs. Flatting out of position with a weak ace is the timid line and realizes its equity poorly.
What happensYou make it 1,800 (9 BB) and he lets it go. You won't always get the fold - sometimes you play a flop with the worst of it - but against a range this wide the reraise shows a profit whether he folds now or calls.
A button that steals relentlessly hands the blinds a license to reraise light - A-5 suited blocks his best aces and flops enough to survive when called. Refusing to defend just lets him print.

Fight back against players who open too many hands by three-betting light - pick holdings with a blocker and post-flop playability so you fold out their range yet still function the times you're called.