Here's a Christmas ornament that hides a secret compartment. Use it to conceal a special gift on your tree!

This is a remix of my own design. I've converted it from a simple Christmas ornament into a secret gift box that still looks like an ornament. The default size (100%) is twice the size of the original. To convert it, I've filled in the diamond-shaped holes on the outside and created a spheroidal interior compartment. I've designed it so the bottom half has an inset that snaps in place much like commercial plastic Easter eggs.

Every year, my father would hide a gift for my mother in a small stocking-shaped ornament on the tree. (And every year she would forget to check the ornament.) I thought I'd create something that would allow others to join in this tradition.

I've provided my STLs, PrusaSlicer 3MFs, and Prusa MK3S+ GCODE to make it easier for you to print this with good quality light enough to hold a gift and still hang nicely on a tree. I've provided 3 sizes: 100%, 75%, and 50%. The 50% version uses the 75% STLs.

NEW: It's all about presentation. So, I've added inserts for the bottom half to allow you to present your gift in the best possible way. They are a friction fit an designed to be loose enough to easily remove. That said, you may need to enlarge or reduce them slightly based on your printer's accuracy. I've included inserts for earrings for all 3 sizes of ball as well as blank inserts that you can modify using simple boolean operations to create holders for everything from a bracelet to a ring to a Benchy.

I've included a photo of the 75% ball with the dangly earring insert. It shows the insert covered in self adhesive felt. This is great for jewelry or anything else that might get scratched by rubbing up against PLA.

How big are the gift balls?

Below are descriptions of the balls, but if you're still not sure, try printing a hollow insert. That will tell you the diameter. The hollow inserts take between 15 minutes for the 50% and about an hour for the 100%.

50%

• Small, but practical. Can hold a bracelet chain and a men's ring with room to spare.
• Interior: about 33mm x 33mm x 40mm
• Weighs 12g with my settings
• Prints in about 3.5 hours

75%

• Standard Christmas ball sized. Can hold a flexible necklace.
• Interior: about 49mm x 49mm x 60mm
• Weighs about 30g
• Prints in about 7.5 hours

100%

• Large. Holds two Benchys with room to spare (you can almost fit 3) - or a heavy, semi-flexible neck chain. You could fit a few Hot Wheels cars - or the key to a real car.
• Interior: 67mm x 67mm x 80mm
• Weighs about 55g
• Prints in about 12.5 hours

The two pieces snap together easily and come apart with a twist. If yours is a little stiff, you can gently sand the tabs that lock them together. Really stiff? Reprint the with increased elephant foot compensation, level your bed, decrease flow, or decrease temp. You could also scale the bottom half slightly (maybe 0.25%) - but only in the X and Y. Do not scale Z or the pieces will not lock in place.