A lock mechanism for securing an expansion card in a computer chassis includes an elongated structural support, a wedge, and a channel structure. The elongate structural support comprising a first and second arm extending obliquely away from each other from a central pivot point positioned between a first and second end of the elongate structural support. The wedge protrudes upwardly from the first arm at the first end of the elongated structural support. The wedge is configured to engage with a riser card component of a riser module including the expansion card and cause a rotation of the elongated structural support about the central pivot point from an unlocked to a locked position. The channel structure extends from the second arm at the second end of the elongated structural support. The channel structure is configured to secure the expansion card with the elongated structural support positioned in the locked position.