Switchable rocker arm

A rocker arm includes an outer arm having a first wall surface, a second wall, and a third wall surface together forming a lock member channel. An inner arm selectively pivots relative to the outer arm about a pivot axis. A lost motion spring biases the inner arm to pivot relative to the outer arm in a first direction about the pivot axis. A lock member is located within the lock member channel which moves along a lock member axis between a coupled position which prevents the inner arm from pivoting about the pivot axis and a decoupled position which permits the inner arm to pivot relative to the outer arm. A lock member retainer is spaced apart from, and opposed to, the third wall surface such that the lock member is captured between the lock member retainer and the third wall surface.