A hinge question is a carefully designed question that enables you to determine whether your class is ready to move on to a new topic/subtopic.
There are a few key rules.
i) It must be solvable in under 2 minutes
ii) you must be able to assess the students’ answers within 30 seconds
iii) the answers the students give must provide you with information that tells you straight away what their line of thinking is – so you can better fix it.