  A periodic $4a \times 4a$ density of states (DOS) modulation (a "checkerboard
pattern") was observed with STM in $\rm Na_{x}Ca_{2-x}CuO_2Cl_2$ (NCCOC) [T.
Hanaguri \emph{et al.}, Nature \textbf{430}, 1001 (2004)]. Its periodicity is
the same as that of the "stripe" charge order observed with neutron scattering
in $\rm La_{1.875}Ba_{0.125}CuO_4$ (LBCO) [J. M. Tranquada \emph{et al.},
Nature \textbf{429}, 534 (2004)] and $\rm La_{1.48}Nd_{0.4}Sr_{0.12}CuO_4$
(LNSCO) [J. M. Tranquada \emph{et al.}, Phys. Rev. B \textbf{54}, 7489 (1996)].
An obvious question is whether the "stripes" are actually "checkers".
Unfortunately, because NCCOC samples are small and LBCO samples do not cleave,
neutron and STM measurements cannot be carried out on the same system. To
determine the relationship between stripes and checkers we used resonant soft
x-ray scattering (RSXS), previously applied to LBCO [P. Abbamonte \emph{et
al.}, Nature Physics \textbf{1}, 155 (2005)], to study single crystals of
NCCOC. No evidence was seen for a $4a \times 4a$ DOS modulation, indicating
that the checkerboard effect is not directly related to the stripe modulation
in LBCO. Our measurements suggest either glassy electronic behavior or the
existence of a surface-nucleated phase transition in NCCOC [S. E. Brown
\emph{et al.}, Phys. Rev. B \textbf{71}, 224512 (2005)].
