Hooking is a fault in anchored casting: the D loop swings around and behind the caster instead of forming behind the rod tip and over the anchor. The name has nothing to do with hooking a fish. It describes where the back loop went.

A D loop is the rounded back-cast loop between the rod tip and the anchor, and the D-loop sweep is the casting stroke that starts it forming. When that sweep carries the line around the caster rather than straight back behind the tip, the loop ends up behind his body. On the exam’s roll-cast fault list the same fault appears as the D loop placed directly behind the caster.

That is more than a cosmetic flaw. The loop the forward stroke is supposed to deliver is no longer hanging behind the rod tip over the anchor, so the delivery starts from a line layout the caster did not choose, and the cast goes where the line happens to lie.

You will not judge it reliably from the side: hooking, tracking and casting across the anchor are all hard to see from a side view. Walk around and look from close in front of or behind the caster. Then correct the sweep, not the delivery — bring the rod back and around under control, stop with the line behind the tip over the anchor, and only then deliver.

Source

From the FFI Fly Casting Definitions (August 2025), Hooking and D Loop; the roll-cast fault list is in Task 19; terms follow the FFI Fly Casting Definitions (Hooking, D Loop).