Typically for small engine where the engine speed is adjusted:
T handled lever(or other shape) that pulls/pushes on the cable that goes to the linkage mounted on the engine that connects to the governor linkages. There is a way to adjust the friction or resistance at the lever. The friction or resistance is what holds the throttle position.
The newer ones have an adjustment bolt to tighten to increase the resistance. Older ones with out an adjusment bolt may require adjustment with a hammer and punch or other ways of pinching the pivot point.