One of the most natural organic garden pest control ideas you can use to help stop a snail is hair - human or animal hair. It even works in controlling slugs. Imagine that!
If you are 'hair challenged' fear not.
Ask your local hairdresser or pet groomer for supplies. I imagine they would be more than happy to see the fruits of their labor being used for such a worthy cause.
I have used this natural method and can say it worked quite well for a while.
After grooming our giant schnauzer I placed his dry hair around some new lettuce plants. (As you know snails can't resist a young juicy lettuce so I thought that was going to be a real test of this method)
I had a reasonable amount of hair and was able to extend it out about 5 inches from the base of the plant so it was good coverage. Because there was a fair amount of hair it held together well and did not blow away.
One of the problems I had was that my dogs hair was really really soft, fine and not that long. I do think if I had used human hair about 6 inches long I would have had a better result.
However, I did find after rain the hair became flat and wet. Once this happened to the hair I used it was rendered useless as it never gained the necessary 'bounce' again. The snails were then able to wander over the hair onto the plants so it was not that effective when I needed it most.
I do still use this method though and sometimes mix egg shells with the hair as the eggshells are not effected by rain. It is not a slug killer but certainly helps deter them.