A slider or slide phone is composed of usually two, but sometimes more, sections that slide past each other on rails. Most slider phones have a display segment which houses the speaker used for calls and the phone's screen, while another segment contains the keypad or keyboard and slides out for use. The goal of using a sliding form factor is to allow the operator to take advantage of full physical keyboards or keypads, without sacrificing portability, by "retracting" them into the phone when these are not in use.
The Siemens SL10 was one of the first sliding mobile phones in 1999. Some phones have an automatic slider built in which deploys the keypad. Many phones will "pop out" their keypad segments as soon as the user begins to slide the phone apart. Unique models are the 2-way slider (sliding up or down provides distinct functions) such as the Nokia N85 or Nokia N95.
A version of the slider form factor, the side slider or QWERTY slider, uses vertical access of the keyboard on the bottom segment. The side slider form factor is primarily used to facilitate faster access to the keyboard with both thumbs. The Danger Hiptop and the Sony Mylo are two primary examples.

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