The WRIntCastleFreePillar02 is empty both sides ....
If you need to, you can stick a plug on the end. There are plugs in the WR kit. Just scale them to suit.
[Edit]
Anyway, how the hell are you going to get up that high ? The kit piece is not suited to be used horizontally.
I should add that it doesnt have any collision, so put a collision box around the base.