Whats a round tuit ?

We have a phrase in Sheffield when asked by our better halves if we have done something we should have done, days, weeks, even months ago... the male Sheffielders reply with "I haven't got a round tuit yet", so whats the solution ? I was given a steel plate with the phrase "A round tuit" written on the front, so now I've no excuse for not doing things and given that most of my musings are generally road related and that our roads in the UK are generally have no vision, it seems like a suitable name for a page...