nailing jelly -->
like nailing jelly to a tree
computing dictionary

<jargon, humour> Used to describe a task thought to be impossible, especially one in which the difficulty arises from poor specification or inherent slipperiness in the problem domain. "Trying to display the "prettiest" arrangement of nodes and arcs that diagrams a given graph is like nailing jelly to a tree, because nobody's sure what "prettiest" means algorithmically."

(01 Mar 1997)