##### A door hinge that allows the door to clear more of the doorway

A conventional hinge rotates around a hinge pin between the two surfaces (in the case of a door, these are the door frame and the door itself). When a conventionally-hinged door is opened 90 degrees, the doorway is still partially obstructed by the door (now rotated through 90 degrees). To fully clear the doorway, the door must be opened 180 degrees.

```                                         |      |                |#
| Door |           Door |#
|      |          ______|#
______  O  ______                ______  O######           ______  O
|# #|                            |#                        |#
Door  |# #| Door                 Door  |#                  Door  |#
Frame|# #|          _______\     Frame|#       _______\    Frame|#
|# #|                 /          |#              /         |#
|# #|                            |#                        |#
______|# #|______                ______|#                  ______|#
```

An offset hinge moves the hinge-pin further away from the doorway than the thickness of the door. It only needs to be opened 90 degrees to clear the door from the doorway. It does, however, need more space for the door to open into. When opened 90 degrees, the door is extended both parallel and perpendicular to the door frame by the offset of the hinge. When opened 180 degrees the door is extended parallel to the door frame by twice the offset of the hinge. Offset hinges are commonly used in converting existing doorways to accomodate a wheelchair or zimmer frame user, in the case that the door can only open 90 degrees, and is only slightly too narrow. If space is really at a premium, a pocket door may be a better solution.

```                                  | Door |
|______|
#######
#
#
#               |#
#          Door |#
#########                       #         ______|########
0         #                      O                         O
#######  # ______                #######                   ########
|# #|                            |#                        |#
Door  |# #| Door                 Door  |#                  Door  |#
Frame|# #|          _______\     Frame|#     _______\      Frame|#
|# #|                 /          |#            /           |#
|# #|                            |#                        |#
______|# #|______                ______|#                  ______|#
```