A checklist line is a single ITEM on a list of tasks or items that need to be completed. It is typically used to ensure that all necessary steps are taken in order to complete a task or project. Checklist lines are often used in the workplace, especially in industries such as IT, where it is important to make sure that all steps are taken in order to complete a task correctly. The term 'checklist line' is made up of four letters: ITEM.