Essentially, this will snap the part to a 5x5x5 grid (or whatever grid size you desire). You can try using this in combination with the furniture system you already have, and hopefully everything goes well.
okay sorry for the late reply. i procrastinated. one question. so i used your script and it works but i have this gird and each square is 4 studs but when moving a 4x4 block it doesn’t line up to my gird, how do i fix this?