On the bottom of the sheet are indicators which can be put into one of the six slits of the special sur-O-scope indicator module at the distal end of the scope. 

The channel indicators are adapted to the width of the individual channels and are part of the channel wall for best realistic results. This is also the spot with the lowest flow and the highest pollution to give a good representation of reality.
 The upper part with the bigger indicators is used on the inside of the basin and the outside of the sur-O-scope. They can be sticked on each desired surface to provide a more complete picture of the cleaning process.