Hi
The white brackets can be used to change the length of a clip that is on the timeline but only from a join. You can drag the start of a clip to the right to shorten it, or drag the end of a clip to the left to shorten it. (Using the correct bracket) A gap does not form as VP automatically closes the ends of the clips together again.
The process is reversible so a clip that you have shortened in this way can be restored partially or fully using the brackets again.
You can also restore sections of clips you have previously edited out using Split and Delete since this action produces a join where the white brackets appear.. Any linked sound is restored at the same time. If you have unlinked the sound then this is not restored creating a gap. You can however close the gap or use the sound track white bracket.
Note you can't lengthen a clip beyond its full length...but you CAN extend image clips that are on the timeline using the brackets.
Nat