needlestack

plural needlestacks

1. figurativelyA stack of needles. Represents the task of finding one thing among a large number of very similar things.

   Unless their flag of a flower is waving, finding such plants is like finding a needle in a needlestack.

   1988 April 15, James Krohe Jr., “Where Has All the Flora Gone?”, in Chicago Reader, archived from the original on 17 Oct 2011

   1 more example

   In those decades of European peace and unchallenged British ascendancy, this small number of ships was enough to keep watch on the French ports and the major sea routes of the world, but not to hunt for needles in needlestacks and make all slavers and pirates quake with fear.

   2004, Dennis Rumley, Sanjay Chaturvedi, Geopolitical Orientations, Regionalism And Security In The Indian Ocean, page 43