Chassis are covered by cover which is screwed to them. Chassis vary in the difficulty of opening and accessing internal components. While most cases open easily after removing screws from the back where they combine the left, right, and top panels into one piece, but in some chassis method of opening is not apparent. Some require removal of the front bezel to access screws behind it.
In another common style of chassis the left or right side panel only is to be removed. Chassis manufacturers also give manual depicting the method of removal of cover to access components.