It may be opened and closed and normally has pre-defined areas with screws and holes the place all the other Components are alleged to be positioned and hooked up to. Fan headers could be located on the motherboard itself, where the 3 pin connectors can be inserted. For added cooling capability , throwing in an additional fan or two is value it. PC instances might come with followers pre-installed, but if not, it is simple to screw them into fan mounts. Just be positive to align them appropriately and have the blades pointing the right method. Fans can have small arrows on the facet that present which means the blades spin and where airflow will be directed.