With the rubber fitted to the glass, run a legnth of string (4-5mm curtain cord is ideal) around the edge of the rubber making sure that its snuggly seated in the groove, and leaving a tail that you can grab hold of.. place the glass squarly in the appature, you may need help for the next bit, lift the tailgate, or easier still, get in the boot, then, with someone gently pushing the screen directly into the tailgate, pull on the string, you will start to see the lip of the rubber, crossing the lip of the tailgate, as you pull the string, keep your hands close to the glass to avoid ripping the rubber, once all the string has been pulled sucessfully, you will then need to "bed" the screen, by gently, but firmly slapping on the glass, all around the outside edge, you'll see the glass move into the correct position (just a few mm's) You may want to spray some WD40 onto a rag, to run round the edge of the rubber, just to help the rubber seat a little easier before fitting

Thom