"do not glean it": Which are "gleanings"? Those which have neither "arm" nor "dripping." If they have "arm" but not "dripping" or "dripping," but not "arm," they belong to the owner; if not, they belong to the poor. ("do not glean it) after you": whence we derive that they are subject to shikchah.
"after you": whence we derive that they are subject to peah. From here they ruled: What is shikchah in an arbor? All that he cannot stretch out his hand for and take. And in runners (grapes growing in a row on isolated vines), whatever he passes by.