I learned this opener and closer trick from Linda Sue Park, at a conference many years ago. Not that many years, but more than I would like to count.
The first and last sentence of your story make the first and last impression on your reader for the time that they inhabit your story world. The reader opens the book and takes the first breath of your story, and is enraptured all the way to the last sentence, when they exhale for the final time before closing the book and saying goodbye to your characters and their journey.
When you have finished your work, there’s a good chance you know what your last sentence needs to be. Or maybe your first sentence is perfect and you’ve kept writing two pages beyond where you should have stopped because you can’t find the ‘just right’ words. Consider that you already have the inspiration you need to create this purposeful art. The opener introduces the reader to the initial character perspective, the closer demonstrates the new, hard-won perspective. Take a look at Cormac McCarthy’s Blood Meridian for an opener/closer duo.
Alternatively, if you have a great opener and closer, check that your character journey has come full circle from a normal world to a new normal post-story turmoil. For a movie version, take a look at Finding Nemo (post-prologue), where Nemo’s father is first terrified to allow his son out of the home, to the much more relaxed closing scene.