This LED-lamp from manufacturer "SELECT Plus" is sold in germany in "Action"-stores. It is imported from china via belgium, and is sold in belgium and the netherlands, perhaps more countries. It is very cheap, price about 4 Euros with 4 Watt and a length about 30cm. These adapters fit into the lamp and make it possible to fix this lamp on shelfes without drilling or glueing. It may be glued with a small piece of double-faced adhesive tape. The files contain three kinds of pieces as stl-files, in 20mm, 10mm and 5mm. It depends on your need which one to use, the 5mm-parts do a good job. The freecad-file is added if you cant get the thing snapped on to your lamp, perhaps your slicer creates a different sizing or your lamp may be different. In this file, there is a drawing where you can edit some length. Two parameters are namen "WICHTIG1" and "WICHTIG2", they define the distance between the two hooks snapping into the lamp and the thickness of your shelf. The size of the thing can be edited by altering the "Length"-parameter of the invisible thing named "Pad". It is set to 5mm in the original file. If you want to use the freecad-file, just select the "LampenHaken" and export it as a stl-file.