This is like the SJTs and the questions asked are designed to find out how you are suited to the role. You will be given various scenarios and will be asked to rank your answers.
During this day you will undertake a series of different tasks and roles within the company both on the shop floor with staff and also in a managerial position dealing with complaints and the like. You will be observed throughout the day on how you perform the tasks and handle the various situations you are faced with. It is important that you read up on the company and know what values they hold.