This is a replacement drawer rail mount/bracket. The original part clips into the back of the cabinet via two holes and then the rail has a U-shaped bend at the end which slides into the channel. I made the channel more solid in my replacement to avoid lateral stress breaking the new part as easily as it did the old one.

I printed mine in PLA+ on its side using a 5mm skirt for better adhesion. Printing on its side helps prevent layer separation of the part and also lowers the amount of required support material. I recommend 50% or higher infill because this thing has to support a lot of weight. I printed mine solid (100%).