If you want to catch snails, create a bunch of make-shift "Chinese Tables", or very low table tops. You can make these out of old boards, placed on top of rocks or bricks. There should be about 3-6 inches of clearance under the table. They love to hang off the bottoms of these things, they accumulate there, as if it were a snail trap.
Video: Picking off the snails from the snail trap.