A loose fence section can worsen in wind and eventually pull adjacent posts out of alignment. A small repair is easier when you identify whether the movement is in the panel, rail, post, or ground before adding new screws.
Check the source of movement
Push the fence gently and observe each joint. Look for loose rail fasteners, split wood, a leaning post, and soil erosion around the base. Keep clear of unstable panels and avoid working during strong wind.
Stabilize the section
Support the panel temporarily while removing a failed fastener. Use exterior-rated screws or bolts suited to the material and keep them centered in sound wood. Do not drive a new fastener into a split edge without predrilling where appropriate.
Protect the post
If the post moves in the ground, adding screws to the panel will not solve the underlying problem. Check drainage and the post base, then use a structural repair method appropriate for the fence type rather than burying decay under soil.
Finish and observe
Confirm that the panel is aligned and that gates still clear the ground. Seal or coat repaired wood as appropriate and inspect the section after the next storm. Replace badly rotted members instead of repeatedly patching them.