  We explicitly study how jet substructure taggers act on a set of signal and
background events. We focus on two-pronged hadronic decay of a boosted Z boson.
The background to this process comes from QCD jets with masses of the order of
m_Z. We find a way to compare various taggers within a single framework by
applying them to the most relevant splitting in a jet. We develop a tool,
TOY-TAG, which allows one to get insight into what happens when a particular
tagger is applied to a set of signal or background events. It also provides
estimates for significance and purity. We use our tool to analyze differences
between various taggers and potential ways to improve the performance by
combining several of them.
