There's the square plate that goes above the rail and then there is another washer and nut that goes underneath. With you saying about screws you haven't got the lashing that's supplied with the Beach have you? The Beach has lashings at the ends of the two outside rails but these won't fit the Ocean.
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I bought it from the forum shop and it said suitable for T5/T6 nothing about Ocean specific.
It looks 'on the top plate' like the previous picture you posted ... I assume of your own, though the bottom plate looks more like this picture, I can see the two screws. Looks like there's been some kind of 'mix up' ... think you've 'nailed it'