The Collection of the Ephemera and Grey Literature of the National and University Library keeps patent files that the library has acquired in accordance with the Legal Deposit Law. The patent files are interesting both, from a thematic point of view, as they cover various fields (from printing and bookbinding to industries), and from a historical perspective, because they date back to the period of the Kingdom of Serbs, Croats and Slovenes, and later to the Kingdom of Yugoslavia (from 1922 to 1942). Having identified both aspects, we have recognised the importance and value of this type of material; thus, we developed a plan for cataloguing and digitization of patent files in the Digital Library of Slovenia with the aim to make this type of material as widely accessible as possible. When designing such a large project (around 6,000 items), we decided to include about half of all material in the first phase, due to staff shortages. After reviewing the existing cataloguing rules, we have decided to create a new method of processing this type of material - a collective entry. The cataloguing of the patent files was a challenging assignment, which required cooperation with the National Bibliographic Centre. The employees of the Ephemera and Grey Literature Collection made records in the Slovenian Cobiss catalogue, providing users with the first contact with the material. Cataloguing was followed by digitization and metadata placement in the Digital Library of Slovenia (with the support of the NUK Digital Resources Department). No additional funds were planned for the project, so all stages were developed within the annual budget of the National and University Library. This required flexibility, innovation and team spirit (inter-departmental cooperation). At the end of the project, 3,306 items of material (patent files) were catalogued and digitized that are now freely available to users in the Cobiss catalogue, on the Digital Library of Slovenia as well. In the future, we plan to complete the project by including the rest of the patent files in the Digital Library of Slovenia, and to promote the project (setting up an online exhibition).