also: split field · half-field coverage · quarter-quarter-half
Treating each half of the formation as its own defense, so the two sides can play different coverages on the same snap.
A structure that divides the field down the middle and gives each half its own coverage rule, decided by how many receivers are on that side. Two receivers one way and one the other means the defense can play one thing to the two-receiver side and something else to the single. The advantage is that each side gets the answer suited to what it faces; the cost is that the two halves have to communicate and can be attacked at the seam between them.
split field, half-field coveragea single full-field call, combo coverageNeeds two players who can make a call and trust each other, so it tends to arrive with an experienced secondary rather than with an install week.