Taking something apart? Want to keep the screws from rolling away?
Sewing something and want to keep track of your pins and needles?
Want to track your screwdriver bits?
I did, so I further customized the Customizable Pacman Ghost by jpralves to hold a magnet inside.
It is designed to accommodate a cylindrical magnet just under the top surface. The included stl's were for my own magnet, which measures 1/2" diameter by 1/4" height.
Originally my intention was to insert it during printing, so that it was nice and enclosed. However, magnets being what they are, it quickly attached itself to my hotend. My recommendation if you want to follow this route would be to apply some glue to the magnet prior to insertion.
Thus, my design now includes an option to insert the magnet through a hole in the bottom after printing.
Use the customizer to find your best setup! The "Look Inside" function is so that you can preview how your settings will work. You won't be very happy if you try to print it that way.