Roof Rail Question

I have not taken a close look at the roof rails ......
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Are there plates/blanks/whatever? on the rails that can be removed so a tie-down (or whatever) can be attached to the rail ?
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If so, how are the plates removed (pry off ?) - and can they be removed without breaking and re-attached ?
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There are 4 caps that you will see. The come off by spreading the lower end, then pulling up. To keep from scratching I fashioned a pry stick from a plastic kinfe and I pry from the inside edge. Best thing is to go take a look at the rails and see for yourself.