Bill Of Material:
. 1x 4 mm diameter nut
. 1x 4 mm diameter and 50 mm long cap scew.
. 2 3d-printed parts (3rd part is not perfect but you can try it).

1/ 3D-print the 2 first parts and 3 if you like
2/ insert the nut in ANTI-LOOSE_Phone_0-02-_2.stl
3/ insert the cap screw into ANTI-LOOSE_Phone_0-02-_1.stl side hole
4/ insert part 2 into part 1
5/ attach a line or a metalic ring with a chain,
6/ rotate the screw until your phone is secured.
7/ attach the other end of the line to yourself by any method.