Typical of older homes, but becoming popular again in newly renovated homes as well, is battened and or panelled walls. Hanging anything onto walls such as this will always be dertermined by the spacing of the panels themselves. But beware... as not all of the panels will be symmetrical, due to the location of architectural elements, such as doors, hallway corners, balconies, stairs, etc. This passage way has all of these elements. So the battens that divided up the walls are indeed uneven. this meant that the gaps between each of the pictures was not the same.The strongest visual anchors are that the battens run equally between them, and that they are all exactly the same hight (even when they continued around the corners then carried on over the stairwell).