Disco 2 Rear Door Stay Repair

Can anyone help me with my rear door stay repair. I have a new stay but just cant work out how it works. It has the metal part that attaches to the floor of the rear boot and then it goes to what looks like a sliding mechanism that attaches to the underside of the door. Now how does it work? Does the bit under door slide within the mechanism or is that fixed? I would really appreciate some help on this.
I had one posted from a scrappy and it too looks the same. The mechanism is locked solid too.

The part in the door slides and the doorframe part fits onto a small pivot, held in place by a circlip. Looking at RAVE, it seems like the circlip has to be removed and then the straining strap can be manoeuvred towards one or other end of the slot and it should drop out.

Cheers Brian. The one I bought to replace the old one seems locked in solid too. So I just need to get that bit moving. Once I have that sorted out I can work on how to get the strap fixed to the boot floor.

This picture should give you some idea of where the little spigot for the door strap is:

It's close to the number M76 2935 at the bottom of the picture.

To finish this thread. My strap was folded under the base of the door. It had corroded so much I t would not slide at all. I used a copper hammer and wd40 to get it moving again and will need now to secure it to the little pivot In the boot. Thinking of welding a washer to the top of the pivot. Took about 1 minute to release it,