Hello Ken, the deal with the snail defense is that they don't like crawling over the spikey seed pods - a purely physical deterrent. If you're not familiar with the liquidambar or sweetgum tree, it's the one with maple-like leaves and rough lined bark that drops these seed pods all over. It's quite labor intensive to gather the seedpods, and the neighbors might look at you funny, but so far they seem to be doing a good job of protecting the pea seedlings. I just reseeded a bed of quinoa and built a little seed pod wall around it after the snails decapitated all the seedlings in the first (unprotected) bed, so that will be a true test of their effectiveness. Depending on how frequently you are out in your garden, you may also want to consider trapping/hunting the snails and slugs as part of your control regime.