Single Haul - Pulling fly line through rod guides during either forward or back Casting Stroke.

• Double Haul - Pulling fly line through rod guides during consecutive Casting Strokes, after returning line hand towards rod hand during Pause.

Related terms in Casts and Techniques: Delivery Cast, Mends, Shooting line, Slipping line, Straight Line Presentations, Slack Line Presentations

Practise it: What is the double haul actually doing?

From the FFI Fly Casting Definitions (2025 Edition), reproduced with attribution to Fly Fishers International.