Guitar slides and tone bars originate from the diddley bow, a one-stringed American instrument played with a glass bottle. It was on this homemade child's toy that many guitarists got their start in the early 20th century, and it subsequently became an enormous influence on the blues sound.
Guitar slides are hollow, designed to be placed on a ring or pinky finger, and can be made from a range of materials. Glass has a warm tone with enhanced mid-range, brass is warm with added resonance, while stainless steel is bright. Tone bars are solid pieces of metal designed to be played with a lap steel guitar and usually have an ergonomic handle to increase dexterity.