Slie guitar or bottleneck guitar is a particular method or technique for playing the guitar. The term slide is in reference to the sliding motion of the slide against the strings, while bottleneck refers to the original material of choice for such slides, which were the necks of glass bottles. Instead of altering the pitch of the strings in the normal manner (by pressing the string against frets), a slide is placed upon the string to vary its vibrating length, and pitch. This slide can then be moved along the string without lifting, creating continuous transitions in pitch.