The cap that covers where the rails meet should be screwed on, and the rails screws will be under that cap.

My pool has a single screw in the side of the upright securing the cap.

Under the cap there are two screws on each rail end, screwed into the plate on top of the upright.

Doubt there is much difference between pools

Try getting one rail off, and see how it goes.

But grab the Liquid Wrench, just in case !!