I designed this to support a 110mm side bookshelf speaker that mounts on a screw head. The middle hole is 3mm in diameter to screw into. The other holes will mount into the wall. Use wall mates or toggles for extra strength. I suggest 60mm + length screws with 5mm thickness. They holes are counter bored too so a head will sit in flush.

Print either as positioned or sideways for no supports.