The Hollywood stars are both keen golfers and regularly head out for a round together.
Zeta-Jones, 53, previously let the cat out of the bag about their racy rule and it came up as Douglas talked to The Guardian.
The Ant-Man star, 78, didn't beat around the bush and confirmed that they do have their own cheeky way of playing when they hit the course.
Explaining how it works, he said: “The rules are I have to whip it out if I don’t hit it past the ladies’ tees, which I manage most of the time.
“But there have been times when we’re playing alone, and have to give her a little show because we are competitive.”
“But only when I play with my wife,” added the Falling Down star.
Douglas and The Darling Buds Of May star Zeta-Jones tied the knot in November 2000 and they share son, Dylan, 22, and 19-year-old daughter Carys.
The pair often share romantic messages on Instagram, with Douglas sharing a snap of them on Valentine’s Day as he wrote: “Happy Valentine’s Day to my darling Catherine! I love you so much .”
In November, Zeta-Jones posted a picture on her account of them kissing on a beach as they celebrated a marriage milestone.
“22 years and 1 day!” she wrote.
“It’s in the fine details... love you sweetheart.”
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