Bottom of closet Door plastic "insert"

This "insert" fits within the sliding closet door bottom and contains a spring loaded peg that protrudes along the bottom edge of the door and uses the spring pressure toon the peg that pushes downward to keep the bottom of closet door into a metal channel. The insert is encased inside the door ends, and a single screw hole(actually allows adjustment of the insert up or down) in the door. These are old sliding doors of a closet, in a house built around 1975.