  The penetrating power of X rays underpins important applications such as
medical radiography. However, this same attribute makes it challenging to
achieve flexible on-demand patterning of X-ray beams. One possible path to this
goal is ``ghost projection'', a method which may be viewed as a reversed form
of classical ghost imaging. This technique employs multiple exposures, of a
single illuminated non-configurable mask that is transversely displaced to a
number of specified positions, to create any desired pattern. An experimental
proof-of-concept is given for this idea, using hard X rays. The written pattern
is arbitrary, up to a tunable constant offset, and its spatial resolution is
limited by both (i) the finest features present in the illuminated mask and
(ii) inaccuracies in mask positioning and mask exposure time. In principle, the
method could be used to make a universal lithographic mask in the hard-X-ray
regime. Ghost projection might also be used as a dynamically-configurable
beam-shaping element, namely the hard-X-ray equivalent of a spatial light
modulator. The underpinning principle can be applied to gamma rays, neutrons,
electrons, muons, and atomic beams. Our flexible approach to beam shaping gives
a potentially useful means to manipulate such fields.
