Suppose a song is in the key of F# minor, as soon as a player finishes his/her climatic phrase, the chord is going to perform a perfect cadence, switching from C# to F#. The verse will begin on F# again.
C# -> F#m -> F#m (verse begins)
Here's a concrete example, timestamp 01:25.
Right before the verse begins, the player would perform a glissando that approximately drops from F# (14th fret low-E string) to F# (2nd fret) and then enters the F#m power chord to start the verse. I've only seen this technique done in Rock settings (with heavy distortion), not sure if other genre does similar technique?
In general, is glissando required to start and end on specific notes of a scale? I think "required" is a strong term in music. Let's say "preferred".
(EDIT: Further clarified the question by rephrasing it)