Gather: this would be by hand.
You shall not glean it afterwards: they were not to go back and pick the clusters that had been left.
For You shall remember …, see verse 18.
Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on Deuteronomy. (UBS Helps for Translators). New York: UBS, 2000. For this and other handbooks for translators see here .