In article ,
The Natural Philosopher writes:
My favorite way on UK style cabinets, which have a 12mm or so gap
between the backing cardboard - or hardboard - and the wall,

IKEA cupboards don't (except the ones to go over fridge/freezers
which have a ~2" gap for ventilation).

Most of the weight is taken on the top of the cupboard where it rests on
the plate.

Not sure the fixings between tops and sides of the cupboards
are designed to take full weight of a cupboard and its contents.
As designed, the weight is taken by the side panels, which is
why I suggested fixing the support to the brackets which are
intended to take the weight. If a bottom support rail is added,
then using the top of the cupboard would be OK as it wouldn't
be taking all the weight.

--
Andrew Gabriel