This read-write INTEGER, not applicable to the Packet Processing Engine and not preserved across a reboot, controls whether a given module should be used, though a module that fails diagnostics won't be used regardless of this setting. An admin sets this to administratively take a specific slot's module out of service without physically removing it. For example, setting this to not-use on a module suspected of causing instability lets the admin temporarily remove it from service for testing, though the setting reverts on the next reboot.