Closure ensures that the objectives are met and applied, as students reapply or label the lesson for themselves. If a summary is necessary, at the very least let students do it. Closure is a commencement of life in light of the lesson. With closure you pass the torch to the learners, who are now the doers and teachers of the objective. Closure is not a teacher activity, but an act of the learner.
Closure refocuses students' attention on the objective.
Answering a question related to the objective, or performing an activity that confirms mastery of the objective gives students the opportunity to recognize what they have learned. Closure is like looking back upon the trail so that one knows which way one has come. To allow students to demonstrate their successful engagement of the lesson. If a summary is necessary, ask students to do it. To make sure they know which train they were on, and where they have got off.