Beer...
in little saucers. All around your garden.
Best snail-killer known to man. Snails are attracted to beer. They drink it and die happy.
Salt works too, but it tends to disturb the soil chemistry. See also, "Roman conquest of Carthage".
We have used it, but find the feral cats will also drink it. Nothing meaner that a 15-lb. barn cat hung over from a garden binge... ;)
Regards, and do you like escargot?
Mary Anne