A side bar for, originally, an IKEA shelf, but can be used for any shelf. The full part is made of 2x outer pieces on the sides and one inner in the middle. The design assumes you glue them together with e.g. 2-component epoxy resin as it's meant to be a static single part in the end.

The IKEA shelf was too deep to have my LPs rest on the vertical legs of the shelf so I had to make a horizontal bar to support them with. Worked fairly well in the end.