We designed pictograms for the non-fiction books in the Elementary school Heroja Janeza Hribarja Stari trg pri Ložu and the library of the subsidiary Elementary school Iga vas. The purpose of pictograms is to make searching materials on the bookshelves easier for library users. We also checked their usability. Pictograms were designed based on the needs of the individual library. We only followed some guidelines from the reviewed literature because there are no general guidelines for designing pictograms. The usability analysis was performed on a sample of thirty-six users who were students of the Elementary school Heroja Janeza Hribarja Stari trg pri Ložu. We made a usability test where they tested themselves in searching library materials using new bookshelf marks. After that, we determined their usability with survey questionnaires. We determined fifty-six subgroups of the Universal Decimal Classification, for which we designed pictograms. We found out that designing pictograms requires a good knowledge of the book collection and library users, and that this is a process that requires a lot of planning. For optimal usability of pictograms, we must also adapt the motifs to the users and library materials. We found out that we achieved the central goal of the task, so we designed appropriate pictograms that help library users searching materials, according to the findings. Although it would be difficult to design universal pictograms, our findings may be useful as a guide for designing pictograms. The pictograms presented in the graduation thesis that we created can be useful as a draft or idea for designing similar pictorial marks of library materials.