Grabbing mechanics

[worldly zenith]

it's a game in which you have to move around, and manually move your arm to pick up objects. you move the arm by pressing the right mouse button and pick up an a item by pressing shift (i'm only working on the right arm a.t.m) when the arm hovers over an object you press shift to pick it up and to let it go again

i got the moving of the player and the moving of the arm figured out (used this tutorial: https://www.youtube.com/watch?v=6hp9-mslbzI&list=PLPsHl7q-58NMZuBcgpKOY6tCObZgn_vsn&index=1&t=211s), it's just the grabbing i'm having trouble with. i've been told to take a look at the fixed joints, but i don't see how that can help the grabbing situation