I surrounded my vegetable raised bed by copper pipe, so soon I'll have an answer to my own question. In the meantime, I'm wondering if anyone else has used this method or otherwise have information about it. Because I live on the edge of a wild canyon, we get literally hundreds of snails and slugs a day. I injured my shoulder last summer throwing them back into the canyon! I don't want to use snail bait and could never put out enough fruit or beer to collect them all. My next move is to try nematodes (spelling?)... Thanks!