  It is now well established that stellar winds of hot stars are fragmentary
and that the X-ray emission from stellar winds has a strong contribution from
shocks in winds. Chandra high spectral resolution observations of line profiles
of O and B stars have shown numerous properties that had not been expected.
Here we suggest explanations by considering the X-rays as arising from bow
shocks that occur where the stellar wind impacts on spherical clumps in the
winds. We use an accurate and stable numerical hydrodynamical code to obtain
steady-state physical conditions for the temperature and density structure in a
bow shock. We use these solutions plus analytic approximations to interpret
some major X-ray features: the simple power-law distribution of the observed
emission measure derived from many hot star X-ray spectra and the wide range of
ionization stages that appear to be present in X-ray sources throughout the
winds. Also associated with the adiabatic cooling of the gas around a clump is
a significant transverse velocity for the hot plasma flow around the clumps,
and this can help to understand anomalies associated with observed line widths,
and the differences in widths seen in stars with high and low mass-loss rates.
The differences between bow shocks and the planar shocks that are often used
for hot stars are discussed. We introduce an ``on the shock'' (OTSh)
approximation that is useful for interpreting the X-rays and the consequences
of clumps in hot star winds and elsewhere in astronomy.
