This is a trim piece to dress up the floor bracket for a bi-fold closet door; specifically this bracket (Prime-Line N 7534 Bi-Fold Door Hardware Repair Kit). I designed it to fit nicely into a cutout of my 6mm-thick flooring, so that the underside of the top lip is flush with the top of the flooring.

My print profile uses supports for the lip with an interface layer. In my case, the trim piece is printed in PLA-CF, and the support interface is printed in PETG, so the support separates cleanly. You can adjust this in the Support Tab / Filament for supports: Support/raft interface. Alternately, the model could probably be printed standing up on the narrow/flat end with no supports, though the lip may not print out as well.