Using eggs shells is a commonly suggested, natural solution for garden slug control. The suggested advice is to crush the shells into small, jagged pieces and sprinkle them around your garden to create an egg shell barrier.
Slugs have very soft bodies and will hesitate to cross an egg shell barrier because of the threat the sharp [...]

Diatomaceous earth is a fine powder that is commonly suggested as a method of slug control. It is made up of the sharp, jagged remains of tiny sea creatures and it works by lacerating the soft bodies of slugs as they crawl over it, causing them to dehydrate and die.
The effectiveness of using diamataceous earth [...]