# It happened that

This phrase marks an important event in the story. Jeremiah wrote God's prophesies on a scroll but the king burned it. It is possible this action was intended to be understood as representing the definitiveness of these prophecies.  

# columns

these are columns of words on the scroll

# would cut it off

"would cut that part of the scroll off"

# with a knife

"using the kind of knife that scribes use"

# until all of the scroll was destroyed

"until the scroll was completely gone"