Hi everyone, I have picked up 2 small raised planter boxes that are made of Merbau. The bottom of the box has aluminium pieces (I think they were some sort of patio roofing that will allow water to drain. I don't know what I should line the planter boxes with. I've been told to double line it with weed mat or some sort of plastic (not sure if there is a certain type of plastic to use). Many thanks for all suggestions.