Here are some lines utilising a tritone substitution chord within a regular II V I chord progression. Usually a II V I chord progression (in this case in C major) would be this harmonic sequence: Dm7 – G7 – Cmaj7
In the case of these lines however, the G7 chord has been substituted with a Db7. This is the tritone substitution most commonly employed (over the dominant V7) in a II V I progression.
As the G7 and the Db7 chord both share a tritone interval between the notes F and B (Cb) the Db7 chord is considered a good substitution for the original G7 chord.
Enjoy the lines!