Hi @Milko43
Theres a few ways you colud do this. You say its not a building system so is it just like a storage area?
If you need particular items going on particular slots then maybe some collisision boxes placed at the locations on the object you want to attach to. If you dont care what item goes where then a simple trace, find the hit location, then a simple equation on the locations to find the grid area it is in, and the centre of the grid square if needed.
Not sure if im understanding you right so let me know if i did , or if you need some more help