Secure the fan base with a replacement black plastic nut. The nut fastens the base assembly to the fan body, helping the unit remain upright and steady during use. A cracked, stripped, or missing nut may allow the base to loosen, wobble, or shift while the fan runs. Before installation, unplug the fan and place it on a flat, stable surfac...Read moree. Remove the damaged nut and inspect the threads for dirt or wear. Fit the replacement in the same direction and tighten it evenly. Do not overtighten, since too much force may damage the plastic threads. Confirm the size and thread pattern before ordering.