Door hinges, one of the hardware accessories, are used to connect or rotate the device so that the door can be freely opened and closed by hinges. There are many types of door hinges, such as fire rated door hinges, metal door hinges, European door hinges, etc. In general, the hinge is composed of a pair of metal leaves, the distance between hinge and door can be adjusted when installing .One of the characteristics of door hinge is that it can be used according to the space and the opening angle of the door, so that various doors have corresponding extension. Different doors need to pay attention to their size when using hinges.