Fret one is a term coined by Saskatoon band Stallions in reference to the way a guitar is played during an extra heavy section of music. In order to produce a more dissonant sound, the guitarist plays chugs while holding the low E string down on the first fret. In order for it to sound correct the low E string must be drop-tuned to a D.
Examples of bands that have fret ones: Stallions, Blind Witness, Strangers and A Textbook Tragedy.
"Fuuuuck, that fret one made the breakdown balls heavy."
"If Slipknot played on fret one they'd be the perfect band."