Collapse action is a device behaviour that snaps a switch into place, usually using a bistable element. When flipping a light switch, strain on one spring increases until it flips position, pulling down the switch. Collapse action allows you to remove your hand from the switch without risk it falls to the down position, as the force needed to overcome the resistance is too great. The action also does not exert force in the lower position, avoiding the spontaneous rise to the up position that a spring invites.