A block assembly for locking a toothed gear housed in a frame includes a body shaped to couple to a portion of the frame adjacent to the gear for translation in a first direction parallel to an axis of the gear, and a locking block coupled to the body that includes at least one locking tooth shaped complementary to at least one gear tooth of the gear. The block assembly further includes an adjustment mechanism operable, when the body is coupled to the frame, to move the locking block in a second direction that is substantially orthogonal the axis of the gear, such that at least one locking tooth is received between a circumferentially spaced pair of the gear teeth to prevent movement of the toothed gear.