Rocker arms in automobiles are typically made from forged/cast steel, or aluminum in higher-revving applications. In the context of an internal combustion engine, a rocker arm is a valvetrain component that typically transfers the motion of a pushrod to the corresponding intake/exhaust valve. Some rocker arms (called roller rockers) include a bearing at the contact point, to reduce wear and friction at the contact point.

A tappet, or valve lifter is a valve train component which converts rotational motion into linear motion in activating a valve. It is most commonly found in internal combustion engines, where it converts the rotational motion of the camshaft into linear motion of intake and exhaust valves, either directly or indirectly.

Other parts in valve train components, engines, mounting etc. made from forging, casting and bar stock.

A rocker arm assembly is a series of rocker arms in a rocker shaft along with rocker support, springs, washers etc. as a component in an internal combustion engine that helps convert the radial motion of the camshaft into linear motion at the valves. It is typically found in overhead valve (OHV) or overhead camshaft (OHC) engine designs.

The rocker arm assembly consists of rocker arms, which are pivoting levers that sit on a shaft or pivot point. One end of the rocker arm is actuated by the camshaft lobes or pushrods, while the other end interfaces with the valve stem. As the camshaft rotates, it pushes against the rocker arm, causing it to pivot and open or close the valve.

The rocker arm assembly plays a crucial role in the engine's operation by controlling the timing and duration of the valve opening and closing events. Proper functioning of the rocker arm assembly is essential for the engine to operate efficiently and smoothly.