What we hope to show you here is the fact that the glass "sight lines" are not level.
Cast you eyes to the upper part of the window and you'll see that the glass is not level from left to right.
This is because the glass unit on the right is within the opening part of the window whereas the unit on the left is held within the window outer frame.
In some older properties the sight lines follow through both horizontally and vertically and to replicate this we would need to insert a non opening sash into each fixed position.
Because they don't open we call them "Dummy Sashes" and would be supplied without the handle or handle fixing holes. Please click on the picture "Dummy Sashes" to see the effect.