Common Types of Door's Hardware-hinge

Door hinges: For some odd reason, door hinges are typically measured in pairs of hinges. So a door with 3 hinges gets noted as 1 1/2 pairs of hinges. The typical door hinges are plain bearing butt hinges, ball bearing butt hinges, spring hinges (self closing), pivot hinges (located at the top and bottom of the door) and piano hinges (continuous).