Probably not an expensive part to replace with a new one from Audi, but seeing as I had the materials and the time I thought that I'd have a go at repairing the broken clasp on the boot lid compartment on my Avant. This is the compartment in the tail gate where the warning triangle is stowed. It was broken on all but one of the second hand Avants we looked at when choosing ours so it's obviously a common problem.
First off use a file and clean up the broken face. Then use a pin vice (a small handheld drill) and drill three holes into the remainder of the clasp. I used a 1.5mm bit and went for 10mm depth, but what you choose will depend what you are using to create the pins. I was using some carbon rod which I had from some model making but my second option was using a paper clip. The pins are then cut to appropriate length and then superglued in place.
The pins create the strength in the repair, effectively reinforcing the rebuilding of the broken section. I used some two part epoxy putty called 'Green Stuff' and moulded up a replacement section. I didn't know what the missing bit looked like so took a guess on this. A trick here is to use some plastic sheet to get a smooth finish and stop the putty sticking to the work surface you are using. A cut up freezer bag will do the job. If it's not perfect don't worry, but this will speed up the shaping once it has cured.
Having left the epoxy to set over night, it was a case of filing it to shape and then a couple of coats of matt black acrylic paint to finish it off.
Fitted. Finish isn't perfect, I could have spent more time to get it properly blended in and smooth, but as this isn't really visible I decided that this was okay.