The Book-End Concept is really quite simple. For a Master Mason to become a 32° Scottish Rite Mason, he MUST experience the 4° first, the 32° last, and three other degrees that represent a Scottish Rite Core Value.
Some Valley's begin their Reunion or Convocations on a Friday with various Degrees and do not make it a requirement for a candidate to attend until Saturday morning. This of course is convenient and fine for a young man who may have to work on Friday. The Valley will then schedule the 4° Saturday morning. But, if the Valley does have candidates show up for the Friday session, then they must confer the 4° prior to any other degrees. This is where the 4° DVD becomes a valuable tool for Valleys to utilize.