The more so because in a modern apartment on the design doors should correspond to the interior of the premises, and in color and texture coating – furniture, which furnished room. But do not think you can just buy them at the nearest building market: door unit – complex technical product, which you will operate, can be again for decades, and his choice must be treated very carefully. Not needed here and unjustified variance: this tells us folk wisdom and bitter experience of many frustrated customers. On the interior doors in a scientific way what you need to know the buyer, not to make mistakes when buying a product that should have been for many years to decorate his home? First of all – the right terminology. After all, if it does not know the seller, he probably does not know the subject matter, but merely utters phrases learned by rote. Then it is hardly trust his advice. Everyone sees a door several times a day, but nobody has ever wondered whether the very definition of the term. In fact, a door used in buildings – a technical device, which closes an opening in the wall, specifically designed for the passage people and move through it objects or goods, separating the volumes of any two spaces or separating the room from outer space, limiting its unwanted visual and physical access, and slimming air, sound and heat transfer between two rooms or space and the environment. Moreover, the correct name of this device – door unit, which includes a door frame and door leaf.