Disco 4 roof channel nuts

[BigGuy]

Hi folks, this is my first post so tell me if I am doing it wrong...

I have munted one of the captive nuts in one of the channels on my 2010 D4 trying to get the bolt out to then fit a roof rack. The remnant of the bolt has a couple of broken 3mm drill bits in it which makes it impossible to drill out with a larger bit. Does anyone have any clues about where to look on the forum for how to replace the captive nut in the channel? It looks to have a hex shape to it as if it is a fitting of some sort. Do they just unscrew? Info? Videos?

HELP!

[Graeme]

They unscrew. Replacements are available from a LR dealer etc.

P/N AYR500061 stud, M6, roof rack. Google the p/n to see what it looks like.