To check means to give thought to something.

An improvement activity is completed when the result sought in the initial goal is obtained. If the result cannot be obtained, it is often that the work has been done without much thought given to it. Confirm the result of implementation at the workplace, adjust all those parts inadequately done and confirm the result again. By repeating this process, a good result can be obtained through improvement. When we check things, we do not merely look them over. It must be a process through which we rethink and reflect on our own work.

Bron: Kanban - Just-in-time at Toyota, Japanese Management Association