A plank doctor is a professional in the art of plank study. Plank doctors are recruited by organisations to seek out 'planks' in their workplaces. Planks being socially inept, smelly bastards. Plank doctors attempt to cleanse and heal these people, if a solution is not found the plank is usually fobbed off into a ditch.
Do you hear about Jimmy - a plank doctor came and took him away
Jim : Look at that ditch full of those dead planker bastards
Bob: Yeah those bloody plank doctors are mental