Merbau Fence/Screen

Hi, I'm looking at putting up a merbau fence but I'd like to know what is the bet way to fix the merbau to the posts?

I currently have Red gum posts spaced 2 metres apart and will be using 90mm merbau.

Should I be nailing the boards by hand? Screwing or just use a fixing gun?

Also I'm worried that the posts are spaced too far apart and the merbau may twist and warp. I'm thinking of putting a piece of 70mm merbau on a vertical in between the posts to keep the merbau straight and true. Is this recommended?

Any feedback will be greatly appreciated.


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