This is a share from my thingi files. https://www.thingiverse.com/thing:2921716
I realize how simple these designs are. As I was building Iron Man armor I didn't have a means of connecting the pieces I had taken the time to cut and assemble so I created these basic shapes. They can be glued or welded into your armor or parts to make them magnetically latch or add straps into the piece to hold it up.
The magnet holder can have between one (1) and three (3) magnets pressed into them with pliers. A dab of liquid super glue will keep the magnets from sliding forward out of their mounts. The magnets also help keep parts aligned while using a heat gun to mold printed parts.
The magnet latches are weakest horizontally, consider mounting so parts cannot slide apart. More latches, more magnets, stronger connections. My shin plates are solid, I can swing them like a bat without the magnets failing, but if they catch on something, they can come apart.
One is a mount for 8X3mm round cylinder magnets. Example:https://smile.amazon.com/gp/product/B01MZ6EJE2
The second is a mount for one and one half (1.5) inch wide nylon straps. Example:https://smile.amazon.com/gp/product/B008585UMW
With Add Ons:
1.5 Inch (38mm) flat side release buckles:
1.5 Inch plastic triglides:https://smile.amazon.com/gp/product/B003VS8Z5U