  We introduce the sandwich veto detector that was built for the 2008 and 2009
hadron runs of the COMPASS experiment at CERN. During these beamtimes it was
serving as a veto detector for neutral and charged particles outside the
spectrometer acceptance, mostly thought to originate from reactions which
excited the target. We also present first mass spectra from $\pi^-(190\,\GeV) p
\to \pi^- \Kshort \Kshort p$ that were measured in the 2008 hadron run.
