srews
Unless you have rust free nails and you CAN nail you better go for the screws ,the "yellow" ones,"passivated" it says on the packet.SPAX makes the best ones as far as I know,but I am willing to learn,so if you come across others that seem to be better value let me-us-know.They won't cost the world.If you think of painting the timber than you have to treat it before with a fungicide/insecticide.Painted timber (outside) is prone to attacks .
Wine barrels are stored wet (!) and are never treated.But they are not painted either.So a natural look is not only cheaper but also healthier .