What’s fine tuning of the sliding action by pre-load adjustment screws?

Pre-load adjustment screws are the parts with groove on the opposite side of Rack and pinion handle. With using screwdriver, rotates clockwise (right‐handed) to get the gentle sliding action and levorotation (leftt‐handed) gives you quick and smooth sliding action.
MIRUC’s traditional pre-load adjustment functionality allows fine tuning of the sliding action.