This is a traditional style coffin shelf for a gothic/metal themed household, which can be mounted to the wall using nails found in a wall mounting kit. For its purpose, It is quite sturdy with the recommended print settings, and does not bend under the load of some heavier objects I have placed within it.

It is (60 x 22 x 9)cm in overall dimensions at its widest and tallest, each shelf has 14cm of headspace and 8cm of depth, with all walls being at least 5mm thick. Additionally, There are 3 nail mounting keyholes for ease of installation, which have a 5mm in diameter entrance and 2mm wide slots. The entire build is split into 4 pieces in order to print on a common sized bed.

You Will Need:

• 3 nails
• Gorilla glue (gel preferably so you have time to adjust each piece before the glue sets)
• Wood clamps (optional)
• At least one spool of filament

Print Settings:

• No supports or raft
• Orient each piece such that the back is against the build plate
• Use at least 3 horizontal and vertical walls
• Use at least 25% infill
• Use an infill pattern that overlaps itself such as: triangular, stars, or rectilinear
• Use some sort of anti-warping method(s). A 3mm brim and limiting room drafts worked fine for me. Without something of this nature you may find the corners will lift about 1mm. If non print breaking warping occurs however, it doesn't matter much as the majority of backing remains flat and is hidden up against the wall. If your build plate is (220 x 220)mm, you will have to rotate the larger pieces by about 10 degrees on the platter to fit a brim on the build plate.
• Seams on nearest
• Relatively slow external layers
• The rest of the settings will vary depending on what you know makes your printer perform well, the above settings are merely to ensure the shelf's structural integrity and visual clarity.

Assembly:

• After printing, apply a slightly generous amount of glue to one of the shelf faces that come together, with about 1cm of space to the edges to allow the glue to spread out upon compression
• Press pieces together, run finger along edges to ensure they are aligned perfectly. Apply pressure or clamp near the walls until glue sets.

• Repeat for each part until the entirety of the shelf is assembled.

• To mount, put one nail in the wall where you want it to go (this nail will either go in the top left or top right keyhole).
• Slide shelf onto that nail, rotate shelf about this nail until level, then place second corner nail (or marker/pencil) at the top of the opposite keyhole to make a mark in the wall (or just hammer it in, be careful not to hammer the plastic).
• Slide the shelf off and hammer the other nail in. Repeat for the bottom keyhole minus the leveling.
  -Alternatively you can hold the shelf where you want it to go and mark each of the keyholes, then hammer the nails on the marks then slide the shelf over all of the nails at once (I tried this at first, however it ended up being slightly unlevel).
  -To remove the shelf, simply pull it up and out.

Printed on an Ender 3 V2 in PLA, each piece taking about 16 to 20 hours.
Designed to get my crystals off of my window sill where my cats repeatedly knock them down.

In the future I plan on making attachments to segment the shelves and put stoppers on the edge of the shelves to stop things from potentially sliding off (however this hasn't been a problem as the grain of the print doesn't lead off the edge.