Shelling "hard-to-shell" pistachios

It is hard to shell a pistachio when the gap between the halves is just too narrow for one's fingertips/nails.

When I come across this frustrating problem, instead of throwing it away or crushing/smashing it with any metal/hard doobrie, I use half a "shelled shell", insert it into that teeny gap, and twist. Voila! Tender green edged with pink ready to serve.