five bar linkage

marellasunny

I use Gruebler's criterion to come-up with 2 dof's for a 5 bar linkage.This astonishes me,especially after seeing an example of a five bar linkage-a manual hand-held grass cutter/hand-held pliers(spring loaded),its on MIT freeware.

Why do we need to input 2 variables for this system to work?

Can someone explain as to why there are 5 links in a spring-loaded plier?ergonomics?how?