A slider mechanism (414) includes a first element (516), a second element (518) and a biasing device (590). The second element (518) slides with respect to the first element (516) along a path. The biasing device (590) functions as an over-center mechanism, such that external force is required to move the slider mechanism (414) for an initial range of its travel, and stored energy is used to move the slider mechanism (414) along a subsequent range of its travel. The biasing device (590) includes a pair of springs (524, 522) that are under compression. The springs (524, 522) are accommodated in openings (530, 532, 534) formed in the first and second elements (516, 518) and the springs (524, 522) move in a plane of the mechanism (414) to reduce the thickness of the slider mechanism (414).