I don't know how you get snaps into wood, but if I were doing it, I'd just use industrial strength velcro. For the strip that is on the wood, I'd use the adhesive velcro, and then the sew on velcro on the back on each back cushion.

I think the snaps are applied to leather or vinyl pieces that are stapled or nailed onto the wood. If you've seen the snaps applied directly to the wood, you could check an upholstery supply site to see what they used.

I would image they used something like boat snaps, used to snap the canvas cover to the boat.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=2513&familyName=Dot+Snap+Fastener+-+Male