「Person downward thrusting with potential harm」requires GOVERNING:「…to make and administer the public policy and affairs of a state, for example. Exercise sovereign authority over. To control the speed or magnitude of, regulate. To control the actions or behavior of people. To keep under control. Restrain impulses. To exercise a deciding or determining influence on」
[ https://www.thefreedictionary.com/govern 2014-12-18 ]
In practical terms, the Chinese lords constructed patrolled walls and medical inspection gateways at key points around prostitution and brothel districts in an attempt to GOVERN and CONTROL the spread of infectious disease, the lynchpin of epidemic scourges affecting humanity.
Meaning to GOVERN, to CONTROL, HAVING JURISDICTION OVER some area of responsibility or territory as「revolving potential harm」(reinfection) that must be GOVERNED, KEPT UNDER CONTROL. In English also,「lynch」means「at a right angle」as when hanging from a tree limb in order to MAINTAIN CONTROL over others.
「Metal for potential harm」refers to the LYNCHPIN, a VITAL, WEDGE-SHAPED key item used to lock in place on a shaft at a right angle, without which「potentially great harm」can result due to loss of CONTROL and loss of the wheel, and the goods, and those riding, and the yak, etc. After a lynchpin broke or became loose, the whole load on the wagon was dumped. Having the lynchpins properly set enables MAINTAINING CONTROL.
GOVERNING CONTROL, MANAGEMENT TACTICS, GOVERNMENT ADMINISTRATIVE REGULATIONS were ordered BY LAW and enforced during endemic outbreaks of sexually transmitted diseases in the attempt to stem the tide. Infected people were forced to wear a codpiece and loincloth to prevent contagious dripping in public places, and undergo treatment by reaming with a bougie, again and again until symptoms abated. Official records were maintained of the treatment results to enable tracing of an outbreak or resurgence, and shaman brute squads enforced the laws under government authority, going door to door when the need arose (see: 'magistrate, authority' 尹 and 津).

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: variant of 轄|辖, to govern; to control; having jurisdiction over; linchpin of a wheel (archaic); noise of a barrow
Japanese EDRDG: the linch-pin of a wheel, to govern or control, the noise of a barrow
Unihan extended: the linch-pin of a wheel to govern or control the noise of a barrow