Sometimes a bit of beer in a bottle on the side entices and drowns them. I recall putting a squeezed half orange shell upside down leaning on a small stick so they could get in. In the morning slugs were on the shell. They r hard to kill as they are rubbery and slimy. I cut them with a narrow sharp rock or the edge of a brick. Or grind them on a rough flat surface like cement or a fired clay paver.
