G'day Gromit,
I found this little gem on eBay and YouTube - the Skin Zipper Door Skinning Tool STK-21890. It sells for $43.08 from the USA and $45.75 USD for postage. There are also replacement heads available too. Skin Zipper Door Skinning Tool STK 21890 Brand New | eBay
The clip of the Skin Zipper in action accessed 10th of June 2014 from, [ame="http://www.youtube.com/watch?v=gc6UoCe0b8k"]Steck 21890 Skin Zipper - YouTube[/ame]
I am not sure how it would perform with aluminium sheet for a Land Rover door skin?
Kind Regards
Lionel

