  We discuss X-ray line formation in dense O star winds. A random distribution
of wind shocks is assumed to emit X-rays that are partially absorbed by cooler
wind gas. The cool gas resides in highly compressed fragments oriented
perpendicular to the radial flow direction. For fully opaque fragments, we find
that the blueshifted part of X-ray line profiles remains flat-topped even after
severe wind attenuation, whereas the red part shows a steep decline. These
box-type, blueshifted profiles resemble recent Chandra observations of the O3
star zeta Pup. For partially transparent fragments, the emission lines become
similar to those from a homogeneous wind.
