Just exactly what is a friction folding knife?

Friction folders are those that have no springs or locks to hold the blade open, but rather use the force or friction of the handles against the tang of the blade at the pivot area to hold the blade open.  A blade stop pin is in place to keep the blade from traveling past the point of full open.  Since there is no lock in place to prevent the blade from accidental closing, force against the back of the blade when in the open position should be avoided.  These knives are designed to be used as cutting tools only.