The interlock feature on this screen ensures it is fully secure during use and transportation. When the support bar is lifted the case is automatically unlocked allowing the screen to be pulled up. Conversely the casing is locked when the support bar is returned. During use the two support feet (which are otherwise hidden) slide out from underneath the casing. These feet are height adjustable for uneven surfaces. The one way lock on the support bar ensures the screen is fully secure and easily adjustable.