A way of revising which can break a topic down into 12 sub-categories. Questions are worth around 5 marks each and it is suggested that students spend approx. 5 minutes on each question. Lesson totals an hour although worked well as a chunk of a 100 minute lesson. If students can't work out the answer, they should move on after 5 minutes (as they would in an exam) and then possibly return at the end if time. Students write the answers to each question in a chosen box which encouraged them to focus on presenting their workings clearly in a small space. Works well with GCSE students, accessible yet challenging enough for students working at B-A grade. Original Clock Idea from justmaths/mathsgem.