in Russia, after DME bombing the metal detectors were installed at entrances to all rail stations.
Well right to the entrance is a simple wooded desk, one has to put his bags on the desk, go through detector. No effort is made to resolve or even listen to the beeps detector makes. You then take you un-scanned bag off the table and continue :-)
Totally pointless from Pax point of view, but very useful for bureaucracy - appropriation of government funds...