You had to push down on the hood, pushing down on the rear wheels, allowing the converter to slide in, as well as lifting the front end. This lifts the brush roll or as you call it the brush role(???) off of the carpet.
The rear wheel assembly has an arm that extends across the opening for the converter. When you push down it lifts the arm out of the way, you slide the converter in and when you release the pressure on the hood the arm locks the converter in place.
The slide in converter was around in the 40s and 50s, the later convertibles the converter slides in from the back.