The Passthrough slot makes it possible to make enormous prints! You can fit extremely long material in to create spectacular things like furniture.
To use the passthrough, you run the first part of your print, move the material, run the next part, etc. To line up each print with the previous one, you can use a ruler, a jig that you print, or the camera.
Here’s a great post from a customer describing their Passthrough technique: Passthrough Alignment Tutorial with Manual Indexing
And this one shows how a customer worked on a big cut. Matching up cuts on the pass through slot - making a RC airplane
Here’s one of my favorite recent examples from a customer that shows you can make something big: First Passtrough project - bunk bed decoration
I hope this helps!