  We perform a collider search for fatjet signals originating from boosted
heavy neutral and charged leptons with masses between a few hundred GeV to a
TeV. These heavy leptons originate from the decay of heavy gauge bosons with
masses above 4 TeV in a left-right symmetric extension of the Standard Model
(SM), which considers a universal seesaw mechanism for the generation of all
the SM fermion masses. The fatjet signals arise naturally in this model due to
the presence of heavy seesaw partners of the SM fermions which decay to SM
gauge bosons carrying large boosts. We employ substructure based variables
lepton sub-jet fraction ($LSF$) and lepton mass drop ($LMD$) together with
kinematic variables of fatjets to look for fatjet signals associated with
non-isolated leptons. These variables help in reducing the SM backgrounds while
retaining enough statistics for signal events, which leads to a robust
discovery potential at the high-luminosity Large Hadron Collider (HL-LHC).
