Thanks Davdor, the step is a plastic moulding and with it are two stainless cap head screws with nylock nuts which fit into retaining hexagonal cavities, eight in number and at 15mm centres, to stop the nuts turning.These offer a good setting range, and as far as I can see the mast foot is pulled aft against the aftmost cap screw,[after setting] the for’d screw of lesser importance but helpfull when fitting the mast. That still leaves the mystry of the pins at each end. There is a small arrow at the single pin end which I think indicates for’d and so the end with two pin holes adjustment aft. I now wish I’d made a stainless step myself[which is the kind of thing I usually do] but I now have this thing and disinclined not to use it. Let’s see if someone can throw some light on it.