  The helicity of a magnetic field is a fundamental property that is conserved
in ideal MHD. It can be explored in the stellar context by mapping large-scale
magnetic fields across stellar surfaces using Zeeman-Doppler imaging. A recent
study of 51 stars in the mass range 0.1-1.34 M$_\odot$ showed that the
photospheric magnetic helicity density follows a single power law when plotted
against the toroidal field energy, but splits into two branches when plotted
against the poloidal field energy. These two branches divide stars above and
below $\sim$ 0.5 M$_\odot$. We present here a novel method of visualising the
helicity density in terms of the linkage of the toroidal and poloidal fields
that are mapped across the stellar surface. This approach allows us to classify
the field linkages that provide the helicity density for stars of different
masses and rotation rates. We find that stars on the lower-mass branch tend to
have toroidal fields that are non-axisymmetric and so link through regions of
positive and negative poloidal field. A lower-mass star may have the same
helicity density as a higher-mass star, despite having a stronger poloidal
field. Lower-mass stars are therefore less efficient at generating large-scale
helicity.
