  Correlations of polarization components in the coordinate frame are a natural
basis for searches of parity-violating modes in the Cosmic Microwave Background
(CMB). This fact can be exploited to build estimators of parity-violating modes
that are {\sl local} and robust with respect to partial-sky coverage or
inhomogeneous weighting. As an example application of a method based on these
ideas we develop a peak stacking tool that isolates the signature of
parity-violating modes. We apply the tool to {\sl Planck} maps and obtain a
constraint on the monopole of the polarization rotation angle $\alpha < 0.72$
degrees at $95\%$ We also demonstrate how the tool can be used as a local
method for reconstructing maps of direction dependent rotation $\alpha(\hat
{n})$.
