Snails have shells, they travel by extending the length of their bodies along a patch of slippery, silvery slime. They eat any and all garden plants leaving large ragged holes in leaves. They feed at night or on overcast or rainy days, hiding under cover when the sun shines. Eliminate any daytime hiding places near your vegetable and flower bed. Crushed eggshells irritate the bodies of slugs and snails making them a good barrier, also. Sprinkling salt on snails and slugs does kill them, but salt is bad for the soil and can be harmful to growing plants. Snail bait is sold at nurseries.