Ship's Mast
To tie belts to both front doors of a car. Then while speeding, climbing out through the passenger window, grabbing the belts and laying on the hood at high speeds. As seen in the movie Grindhouse.
Kim: owh hell no! you said were were never, ever, going to play ship's mast again!
Ship’s Mast
As the previous commenter said, to ‘play ship’s mast’ is to climb out of the passenger seat of a car with the belts out of both windows and to lie on the bonnet/hood holding the belts while travelling at speed. The film in question is called Deathproof however, not Grindhouse.
“Say you’ll suck him off to convince him to lend us his car and then we’ll play Ship’s Mast!”