"Lateral Inversion" refers to the phenomena in which your left appears as your right and vice versa in a mirror. When a plane mirror is held perpendicular to a plane of paper with the word "POLEX" printed on it, it produces a laterally inverted picture. This occurs because all objects appear upright when viewed from the side but are turned over when seen from the front. In English, we invert letters before they are printed or typed (for example, "dear" becomes "dear"). This process is called "capitalsization." Computer printers avoid this problem by printing upside down; they then flip the page over so that what was once up is now down and vice versa. People who see words laterally inverted often claim that they seem to be backwards or upside down. In fact, they are not; it's just that our brains invert them before we see them. The same thing happens with drawings and photographs; think for example how surprised you would be if you saw a picture of a house without its roof! Mirrors can be used to create images with text that cannot be achieved any other way. For example, a mirror can be used to display book covers in a gallery. The disadvantage is that people will be able to read the texts! The lateral inversion effect has been used in advertising.