Window manifestations are required by building regulations to ensure glazing is safe for people who are likely to come into contact with it.
Manifestations are usually applied to any expanse of clear glass, to make it more visible and reduce the risk of people colliding with it causing personal injury.
Often in the form of rows of small dots or squares made from either frosted or coloured vinyl, regulations state that these need to be applied at two heights. The lower row between 850mm & 1000mm from the floor and the upper row to be between 1400mm & 1600mm from the floor.