r/MegamiDevice:

u/BrimstoneOmega

Some of the newer MG kits have this as well. One side of the joints is on a mini runner that you cut out with an array of the joint halves. You take this segment of runner out, and push the whole array together at once, then cut out the individual wrist joints as one assembled unit.
u/BrimstoneOmega

I use tiny magnets for my warhammer models. You can get darn near microscopic ones here; https://themagnetbaron.com/?srsltid=AfmBOor7FsgyJCBf6oJmiBmZ-7I6jS9y_hxY7nTJ2fGV0dvd-eo7FCUc