They do, and apparently they're hermaphroditic. When they copulate (at least in some species) they first attempt to stab each other with a "love dart." The love dart's purpose is to make the recipients body less capable of killing off sperm. In some species only one snail does this, in others both doe.
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Then apparently they both insert their penises in each other, and whoever's body doesn't kill off all the sperm gets fertilized. Which could be one, both, or neither of them
And for reference:
"You can spot love darts sticking out of snails in mid-courtship, and even find them abandoned in slime puddles where mating has been happening.
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Scale it up to human size and the love dart would be the equivalent of a 15-inch knife, according to Koene. Nonetheless, he’s only seen one snail die by dart.
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“It does make a pretty decent-sized hole in the body,” he said, “but in general, they are fine. They’re used to this, I guess.”"
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Then apparently they both insert their penises in each other, and whoever's body doesn't kill off all the sperm gets fertilized. Which could be one, both, or neither of them
"You can spot love darts sticking out of snails in mid-courtship, and even find them abandoned in slime puddles where mating has been happening.
`
Scale it up to human size and the love dart would be the equivalent of a 15-inch knife, according to Koene. Nonetheless, he’s only seen one snail die by dart.
`
“It does make a pretty decent-sized hole in the body,” he said, “but in general, they are fine. They’re used to this, I guess.”"