Disassembling iRobot Roomba 551 Bottom Plate

Place your Roomba upside-down on a hard surface.

While holding the side brush in place, use a Phillips #1 screwdriver to remove the 4.5mm screw from the center of the brush.

Gently pull upwards on the brush to remove it.

Rotate the Roomba upside-down so the bottom is facing towards you.

Using a Phillips #2 screwdriver, remove the captive screws that hold the bottom plate in place.

Carefully lift the bottom plate.