hinge 
(hĭnj)
(hĭnj)n.
1.
a. A jointed or flexible device that allows the turning or pivoting of a part, such as a door or lid, on a stationary frame.
b. A similar structure or part, such as one that enables the valves of a bivalve mollusk to open and close.
2. A small folded paper rectangle gummed on one side, used especially to fasten stamps in an album.
3. A point or circumstance on which subsequent events depend.
v. hinged, hing·ing, hing·es
v.tr.
1. To attach by or equip with or as if with hinges or a hinge.
2. To consider or make (something) dependent on something else; predicate: "convenient and misleading fictions for hinging an argument" (Stephen Jay Gould).
v.intr.
To be contingent on a single factor; depend: This plan hinges on her approval.
[Middle English henge; see konk- in the Appendix of Indo-European roots.]
hingeleft: strap hinge
right: T-hinge