Not sure about the boards, but you can just tightly wrap the posts and use a lot of staples at the top and bottom to hold them in place. I would not suggest glue because if your cats are like ours, they will eventually rip through the sisal and then you'll have a mess on your hands if you want to replace it. Bobcat (husband) wrapped the legs of his work table with sisal rope. It took a year and a half, but you can see the results in this photo. Halo and Pepper eventually ripped it up.



p.s. That's Pepper "helping" Bobcat with his painting.