one is obviously so you don’t have to reach into the outfeed to grab your work.
Also, a short piece will want to ‘lift’ as the rollers press down on the back end of the workpiece.
On a long board you might see this as a snipe - which is why you support the exiting board
by hand. On a short board you cant do that and if it lifts enough it
will smash into the blades and just chop up your board. there may be other reasons
but these two should be enough. There are plenty of videos that may have better
Having said that - there is a non-recommended way to do it. you start your short board by pushing
it in with a longer board kinda like a train. the idea is that if they are in contact it acts as one long board.
It works ‘most’ of the time for me unless the front board takes a turn. (I only try this at home).
Pieces need to be no less than 1 ft long.
Why is that? Please educate me.