Working further afield than either the Keel or Sloop, the Billy Boy was a Ketch rigged trader with a hull similar to that of a Keel but having high bulwarks and, as a rule, no leeboards. The average dimensions of the type were in the order of 63' x 18' although some had a narrower beam, which, although allowing them to pass through locks on the canals, decreased their sea-keeping qualities.
A well steeved up bowsprit carrying a multiplicity of jibs was a feature of the rig; the masts were both stepped in tabernacles for lowering when the vessels had to go 'above bridge'.
Decoration at bow and stern was common, particularly ship-carpenters carving on the trail boards and around the hawse holes; the gunwale capping was generally painted white, bulwarks black, top strake lined white and brown and hull black. The type rejoiced in distinctive names - 'Joshua', 'Try-on', 'Abeona', 'Bernard', 'Fern', 'Aimwell', 'Eliezer', 'Bottle Imp', 'Tiger', 'Surprise', 'Village Flower' and 'Sandringham' being recorded.