Knapp is a see also of chalcedony.
As an adjective knapp
As a noun chalcedony is
a form of fine-grained quartz that is nearly transparent or has a milky translucence; it fractures conchoidally.
As a adjective knapp
As a noun hinge is
a jointed or flexible device that allows the pivoting of a door etc see also pintel.
As a verb hinge is
to attach by, or equip with a hinge.