Slide guitar is a particular method for playing the guitar. Instead of altering the pitch of the strings in the normal manner, by pressing the strings against the fretboard with the fingers, a slide is used. The slide is a tube of some hard material. Commonly these are made from glass (or a bottleneck, which gave rise to the description bottleneck guitar), although metals (normally steel or brass) are also used. The slide is pressed against the strings (lightly, so as not to touch the strings to the fret board), producing a sustained tone which can be continuously varied by moving the slide across the neck.
In this style the guitar is often tuned to an open chord, such as open D or open G, allowing the player to change chords simply by moving the slide with one hand, without fretting any strings with the other. This method is the easiest way of playing chords in slide guitar, and is most common; but many experienced guitarists use other tunings as well.
Some specialised makes of guitar are commonly used to play slide. These include resophonic or resonator guitars, commonly also known as dobros after the Dopyera brothers, whose company first made them. These guitars are made with steel bodies. Some have a square neck rather than the more normal curved neck and are designed to be played across the knee.
