Jazz GuitarsThe archetype jazz guitar is Gibson L-5 first manufactured in the 1920s. Instead of the familiar round or oval sound holes two F-holes were incorporated into the guitar's top. The steel strings were attached in a trapezoid tailpiece at the end of the guitar body, which resulted in a height-adjustable bridge. The L-5 was also the first guitar that had a total of 14 frets. To counteract the increased string tension, Gibson engineers incorporated a steel rod in the neck up to the saddle. A threaded nut allowed the neck to be adjusted.