the invention relates to a card index which can be fixed to a vertical wall or vertically mounted on a base , in which the index cards are held by means of clamping devices in a receiving compartment formed in covered manner in the upper part of the index casing and are individually released on operating a selection key and transferred into the lower area of the casing provided with a window - like opening for inspection , the cards being secured and locked in the clamping device , so that a reliable release of the selected cards is possible , including those cards made from a material with a smooth surface such as e . g . plastics foil and in which incorrect manipulations are not possible .