A King is not a guaranteed book. The Ace of the same suit beats it, and if the suit gets cut, any spade beats it. Walking a King means playing it in a position where it takes the book — that requires timing, information, and a little courage.
Wait for the Ace to be played
The King is safe from same-suit competition once the Ace of that suit is out. If somebody leads the Ace of Hearts and takes the book, your King of Hearts is now the highest heart on the table. Time to walk it.
If the Ace hasn't been played, leading a King is dangerous — you're announcing you have it, and any opponent with the Ace will take you down.
Watch for voids
Even after the Ace is gone, your King is only safe if nobody at the table is void in the suit. If somebody's already discarded on the suit twice, they'll cut your King with a spade.
The safest walk is early in the hand, before anyone has had time to become void. First or second round, right after the Ace burns, is the sweet spot.
Lead it yourself vs. hope it comes around
If it's your lead and the conditions are right, lead the King. Don't wait for somebody else to lead the suit — they might not.
If you're in second or third seat and the suit gets led, play the King only if the Ace has already come out. Otherwise, duck under with a lower card and hope for a cleaner opportunity next round.
