Do you have brick wall with mortar joints? Are you looking for an effective way to mount stuff to that wall without have to drill holes? Maybe you have some 3D printed art you would really like to mount, and don't want some hook showing.
Well, for under 20cm of PLA and well under 10 minutes, you can!
Make sure you print it orientated like in the pictures. I did mine at 0.20mm layer height. You want 4 layer thickness for the hook section, gives it sufficient rigidity. You also want 3 layers for the section that inserts into the brick, for sufficient flexibility and hold.
Measure your mortar size, mine is around 12mm, and print some ±1mm. Not all mortar is the same size in a wall. Then just put the hooks in until the feel secure.
Force is applied downward on the hook and the bottom brick by whatever you are hanging. The top section is to stop it from pulling out.