I recently found this clutch adjustment tool on eBay.
The plans for making VW 667 are included in the Workshop Equipment for Local Manufacture book, but many tool manufacturers offered them too, including Hazet.
This photo from the Workshop Equipment book shows VW 667 in use -- much easier than fumbling around with a 14mm box-end wrench. Later VWs had a large wingnut in place of the early 14mm adjustment nut, effectively making this tool obsolete. The late wingnut can also be retrofitted to earlier cars, but that just wouldn't be right, would it?