Gedhek, a wall material for Using's house, which is still used in Banyuwangi, Indonesia. The existence of gedhek in The Banyuwangi Community has never been associated with school knowledge. This makes gedhek known only as objects that are dividing the house (wall). Even though the process of making up to installing gedhek contains various learning concepts, especially mathematics. These mathematical concepts need to be identified through a qualitative research framework. Research data obtained by the method of participatory observation, in-depth interviews, and cultural documentation, then analyzed according to the steps of the ethnographic approach. The results showed that in the process of making gedhek, the concepts of numbers and number patterns, geometry, sets, fractions, measuring objects with non-standard units, congruence, transformation, and arithmetic can be found. From these mathematical concepts can be identified the existence of mathematical activities, such as counting, measuring, designing, locating, and explaining.