  This paper considers work extraction from a quantum system to a work storage
system (or weight) following reference [1]. An alternative approach is here
developed that relies on the comparison of subspace dimensions without a need
to introduce thermo-majorisation used previously. Optimal single shot work for
processes where a weight transfers from (a) a single energy level to another
single energy level is then re-derived. In addition we discuss the final state
of the system after work extraction and show that the system typically ends in
its thermal state, while there are cases where the system is only close to it.
The work of formation in the single level transfer setting [1] is also
re-derived. The approach presented now allows the extension of the single shot
work concept to work extraction (b) involving multiple final levels of the
weight. A key conclusion here is that the single shot work for case (a) is
appropriate only when a \emph{resonance} of a particular energy is required.
When wishing to identify "work extraction" with finding the weight in a
specific available energy or any higher energy a broadening of the single shot
work concept is required. As a final contribution we consider transformations
of the system that (c) result in general weight state transfers. Introducing a
transfer-quantity allows us to formulate minimum requirements for
transformations to be at all possible in a thermodynamic framework. We show
that choosing the free energy difference of the weight as the transfer-quantity
one recovers various single shot results including single level transitions
(a), multiple final level transitions (b), and recent results on restricted
sets of multi-level to multi-level weight transfers.
