Qualcraft 2481 Ladder Hook with Wheel, One Hook Provides Ideal Method Of Securing The Top Of A Ladder To A Rooftop, When Used With A Paired Ladder Hook Both Hooks Fit Over The Top 2 Rungs Of The Ladder & Hook Over The Roof Edge Wing Nuts Of Both Hooks Are Tightened Holding The Ladder Firmly In Place Designed To Fit Single Or Extension Ladders Made From Powder Coated Steel For Superior Durability & Strength. Durable and convenient ladder hook with wheel Adjusts to fit between the top two ladder rungs Compatible with wood, fiberglass, or aluminum ladders Compatible with round or D rung styles Two hooks must be used per ladder.