It more than likely has threaded sections bolted through the gunnel wall, if your is carpeted on the inside the carpet will more than likely cover the nuts on the inside look for the lumps in the carpet
Ill have a check, carpet there is flat to look at, but maybe some bolt is countersunk. There was a bit of marine ply on the inside above the carpetted piece, but removing this showed me nothing. Dont really want to peel the carpet off :/
Dont take the carpet up unless you have too, make sure you find the nuts before hand, I have spent many an hour re-gluing carpet for someone else who that he would just pull it up to "have a look"