When a door is placed, where its hinge is depends on what half of the block was targeted when placing it. Hinge placement can be overridden by the presence of other doors nearby, resulting in the hinge being placed on the opposite side of it. However this check does not neccessarily check whether the resulting double door formation is valid, making it impossible to place certain patterns of doors without heavy and unneccessary maintenance.

A purpur block is used here to highlight block halves.

1. Place a door on each half of a block, noting how the hinge position depends on where on the block the door is placed.

2. Place a door next to the target block with its hinges facing that block

3. Note how no matter where the door is placed on the block, the hinge will now always face away from the door, as it tries to form a double door even though the resulting double door is clearly not valid: