What is a hook (half-point) in sports betting?

A "hook" is the half-point added to a spread to eliminate the possibility of a push. Lines like -3.5 or +7.5 are common. The key hook numbers in NFL betting are 3 (field goal) and 7 (touchdown), because games end on those margins most often. Buying the hook around these key numbers — paying extra to get -3 instead of -3.5 — is a common strategy discussion among experienced bettors.