wrote:
Please indicate me whether it means that aircraft manufacturer sell
all aircraft parts to customer. Customer DIY.

A quick-build kit is a kit where some assembly steps have been
done by the manufacturer. Usually, all kits provide the majority
of the components (all the airframe, but the
engines/avionics/instrumentation is often left for the builder to
procure independently).

If you go to the various kit companies websites you can usually get
an explanation of what the quick build kit entails. The VANS RV
quick kits for example, the wings and the fuselage come as entire
units rather than a bunch of pieces of aluminum that need to be
drilled and rivitted. I've seen other qb kits that came all
drilled and cleco'd together and you just had to drive rivits.

The manufacturer on the QB version, spends time making sure they
are still within the 51% rule (the eligibility for
an amateur-built certification is that the build constructs
it for recreation or education purposes. The FAA requires
that a majority of the tasks (not time, but some identifiable
task) be done by the builder.