linchpin /linchˈ or linshˈpin/

1. A pin used to keep a wheel on its axle
2. A person or thing essential to a plan, organization, etc (figurative)

• stockpot
• stockpots
• stockpunisht
• stock-raising
• stock rider
• stock riders
• stockroom
• stockrooms
• stock route
• stock routes
• stocks
• stock saddle
• stock saddles
• stocks and stones
• stock-still
• stocktake
• stocktakes
• stocktaking
• stocktakings
• stock whip
• stock whips
• stockwork
• stockworks
• stocky
• stockyard