This is a generic concept to create a "keyhole" slot for your project that you want to hand on a wall by a screw or nail. The idea is taken directly from the woodworking world, where you would use a keyhole router bit to plunge into a piece of wood, then move along the work piece once the router bit is submerged beneath the surface.
If you use this thing or a similar thing, you can use this as a negative space you can subtract from your wall-hanging thing. Use a boolean "difference" operation... or in tinkercad, assign this object the "hole" color and group it with your main thing.
This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/5rcAYD0KB15