Rob wrote:

I'm about to buy a Neff U1721 built under oven and need to prepare the space
in my kitchen.

So far Ive only been able to find info on aperture dimensions.

I'd like to know how its actually held in place and what I need to provide
within the aperture for the fixings.

I'm reasonably handy with DIY and a bit of a tech head, but have never
fitted a built in oven before. So any tips/advice on what to do or watch out
for would be greatly appreciated.

Presumably you're fitting this inside an existing appliance housing unit?

Built-under ovens normally just sit within their housing, you'll
probably find there are 4 small screws to locate it firmly to the unit
it's sitting in, but no more than that (ie, even if you missed them out
altogether it wouldn't be a big issue.

Of more significance is provision for ventilation and clearance - you
need to ensure you follow whatever the manufacturer stipulates. Also
how you provide it with power, which you don't mention: these are the
issues!

David