Sliding doors
In a machiya, the only solid walls are usually those on the outside of the house. Rooms are, rather than with walls and doors, divided or enclosed by sliding doors. These doors are inserted into guiding rails on the floor and their top, called shikii and kamoi, respectively. In each track are two groves, which can each hold up to two sliding panels, allowing them to be slid over each other. The sliding doors can easily be removed by simply lifting them up and swinging them out of the tracks. Two rooms can thus be enlarged significantly by simply removing the sliding panels between them, creating one large, continuous space. This also helps ventilation in the house and in case of damage, a panel can be replaced or taken out for repair without much ado. On the downside, the panels do not provide any insulation against the hot of the summer or the cold of the winter, and since noise can easily travel through them, they do also not provide much personal privacy.
The two main types of sliding doors are called shōji and fusuma. Their basic structure is the same, as both feature thin wooden strips which are arranged rectangularly and framed by stronger struts. Their appearance and mode of usage, however, are very different.
Shōji (障子)
Shōji have a somewhat lighter feeling to them, because translucent rice paper is pasted only on one side, allowing light to pass through them. Because of this property, they are generally used on outside walls or facing the veranda or corridor of a house, but can sometimes also be found on inner walls if more light is needed to come through. Because they are made of nothing more than wood and paper, they are very light and do not even need rollers or other aids, but can be moved around in the sliding tracks without much effort.
Shōji are generally not adorned and are not used in order to have a decorative effect, although the pattern of the wooden strips and the light that shines through them make for a pleasant aesthetic experience.
Shōji can be divided into three types, depending on how their skeleton is organised. Yokogumi-shōji feature a skeleten where the small wooden strips are arranged in a way that they stress the horizontal line of the pattern. Yokoshige-shōji are similar, but there are more horizontal wooden strips, reducing the space between them and giving the pattern a bit more elegance. Lastly, tatshige-shōji feature relatively few horizontal bars, but a large number of vertical bars, making them look taller than the other two types, although all are of the same height.
Shōji do not need to be completely covered in paper, they can _and often do_ have different additions such as windows, sliding parts and similar features to allow a more flexible usage.
Fusuma (襖)
As mentioned above, fusuma and shōji share the same basic structure. In the case of fusuma, however, both sides are pasted with thick, heavy opaque paper and a lacquered ledge frames it all the way round. Fusuma are generally only used on inside walls, i.e. their purpose is that of dividing rooms while acting as entrance doors at the same time. In contrast to shōji, they can be decorated with either simple patterns or, as is done in many stately and representative buildings, they are adorned with sophisticated paintings.