This model is a hook for paintings designed to be glued to the wall using plaster or any over type of glue.
The back side of the hook is textured to improve the adhesion of the glue.
Depending on the type of glue you use you may want to print your part out of PLA and expose the back side to acetone. Acetone can partially dissolve the PLA top surface and leave a porous microstructure which further improve the adhesion. Two pictures of the PLA microstructure before and after this treatment are included.

EDIT: Following the demand on comment I added a version of the attach meant to be fixed with screws onto the wall. The design uses 3 cone head 4mm screws. If you use it please send me a picture in the "makes" or in messages.

EDIT 2: I added a flat version of the attach in case you want to use some type of double sided tape to fix the hook.

EDIT 3: I added a version for 15mm thick paintings. The original version is for 32mm thick or more.