Moal leeches are tied entirely on a string with a trailer hook at the back. This gives the fly greater action than a fly tied on a rigid hook. More fish are landed with the Moal fly as well.
Custom Moal Leeches are tied by Grabflies.com in the good old USA. Moal's are tied using the best materials on the market and are tied to last (super glue, Berkley Fireline Braid 15 LB (double over for 30 LB strength) quality hooks.
If you had to pick one fly to fish for Steelhead with, highly consider a Moal Leech.