newshound wrote:

Particularly for "ordinary" carcases with a hardboard back. You
either fit a top batten with the hanger type fittings, or some sort of
intermediate batten attached to the carcase that you can screw through,
or a batten at the bottom that immediately ensures that all your units
are horizontal, and aligned vertically.

Rather than fit the two little mounting brackets in the top corners of
each wall cabinet, you can buy it in 2 metre long rails, saves faffing
about measuring where they'll go

https://www.locksonline.com/Cabinet-Hanger-Wall-Rail-2032mm-Long-6492.html