lynchpin, linchpin, focal point, mainspring, touchstone, catalyst, counterweight, cog, pivot, crux, talisman, trump card, keystone, leitmotif, bridgehead, bulwark, microcosm, lodestone, centerpiece, backbone, lodestar, flashpoint, cornerstone, counterpoise, locus, ascendancy, conduit, dialectic, masterstroke, balancer, centering, definer, crucible, metaphor, counterforce, pillar, polestar, cohering, pendulum, prime mover, antipode, wellspring, lightning rod, triangle, perfectibility, periphery, fountainhead, sparkplug, underpinning, whirling dervish, dynamo, hinge, integral, counterpoint, thrust, stalwart, counterbalance, dynamic, locus classicus, unbalance, beneficiary, telos, achilles heel, triumvirate, springboard, orchestrator, bedrock, rampart, embodiment, litmus test, vicissitude, playmaker, galvanizing, hub, fore, catchword, seesaw, rorschach test, launching pad, personification, inexorability, impetus, linkman, referent, leitmotiv, mainstay, equipoise, crossroads, lever, synecdoche, dynamism, centripetal force, confederal, halves, colossus, adaptiveness, formidability, handmaiden, hallmark, interrelationship, midfield, impregnability, prop, groundwork, precondition, foundation, motivator, preconditions, prerequisite, prerequisites, rationale, clement, intermediary, anchoring, locking, alignment, allimportant, appropriate, connect, fusing, homeostatic, ic, starting, switch, unifying, valve, weakest, winch, accelerating, bevel, hydrostatic

., compound lever, dandle board, lever, oarlock, peg, pin, pinch bar, rowlock, seesaw, teeter-totter, teeterboard, thole, tholepin, tilting board

lever

pin, pivot