\input zb-basic \input zb-matheduc \iteman{ZMATH 2012e.00623} \itemau{Villarroel, Silvia; Sgreccia, Natalia} \itemti{Concrete didactical materials in geometry in the first year of secondary education. (Materiales did\'acticos concretos en geometr\'\i a en primer a\~no de secundaria.)} \itemso{N\'umeros, No. 78, 73-94 (2011).} \itemab Summary: This paper intends to identify and characterize concrete didactical materials that can be used for teaching geometrical contents in the first year of secondary education. Such materials are interesting for learning geometric skills and allow to develop and to apply them. The research is theoretically based on the ideas of the realistic mathematics education. Through a qualitative approach of an explorative-descriptive scope seven large groups of materials are distinguished: 2D and 3D fixed models, geometrical puzzles, tangram, geoboard, dynamical transformations, origami, objects of the real environment. These ones, depending on the didactical intention, promote the development of varied geometrical skills. Some examples of tasks are presented. \itemrv{~} \itemab Resumen: Este trabajo se propone identificar y caracterizar los materiales did\'acticos concretos que pueden utilizarse en la ense\~nanza de los contenidos geom\'etricos en primer a\~no de la educaci\'on secundaria. Adem\'as, interesa reconocer las habilidades geom\'etricas que tales materiales permiten desarrollar al ser aplicados. La investigaci\'on se fundamenta te\'oricamente en las ideas que sustenta la educaci\'on matem\'atica realista. Mediante un enfoque cualitativo de alcance exploratorio-descriptivo, se distinguen siete grandes grupos de materiales: modelos fijos 2D y 3D, rompecabezas geom\'etricos, tangram, geoplano, transformaciones din\'amicas, origami o papiroflexia, objetos del entorno real. Los mismos, dependiendo de la intencionalidad did\'actica, favorecen el desarrollo de variadas habilidades geom\'etricas. Sobre esto, se presentan ejemplos de actividades. \itemrv{~} \itemcc{G43 U63} \itemut{concrete didactical materials; geometrical skills; geometry; secondary education; realistic mathematics education} \itemli{} \end