have a twice yearly clean contract water channel to hoover dry with a wet and vac , on a large roof in stockton. having a harness cert would simplify the job, just involves using a wet + vac to dry water channels dry they are abuot 16-18 inches wide, hardly any water in them 800 feet, they need a company letter showing they have been cleaned of exess water twice yearly, for insurance purposes, if this is to be common practice i will get a safety harness cert,. myself. you need to use a harness attatched to a wire rope just for health and safety protocol. its all on a flat roof with a 4 feet side wall around edge so no safety worries. if interested let me know, i am the only company he has contacted so i am 100% i have the job if i can get training or will sell post pics tomorrow