Turn off and unplug the Eureka Boss vacuum cleaner.
Turn the "Brush Roll Control" to "Bare Floor" and push until it locks into position. Step on the foot pedal and lower the cleaning handle to the floor.
Turn the vacuum cleaner over and use a screwdriver to remove the three screws that hold the base plate in position. Set the screws aside in a safe location.
Lift off the base plate. Gently pull the brush roll out of the vacuum and slide the old belt out.
Set the new belt around the left end of the brush roll and loop around the motor shaft. Place the right end of the brush roll back into the vacuum and push gently to secure the brush roll into place.
Turn the brush roll twice to center the belt. Set the tabs on the base plate into the slots on the vacuum and rotate slightly to return to position. Tighten the three screws to secure.