Outside fuse box- positive side

I had to take off positive side to the fuse box to move it to replace the battery. Now, It has been 3 days and I don't know what was holding the positive wire down tight (misplaced nut piece). I called to ask what size nut went on there but they didn't know. I bought 2 nuts that fit on but only screws on the size of the nut size width. So that is not helping. The screw piece that the positive wire goes down on is like 2 inches or so"? Help, I have to secure the positive wire back on the fuse box. Could it be a "wing nut"? I was not the one who took it off, so I don't remember. :(
Please help or can you send me a good picture of the positive wire connected on the fuse box in the engine. I looked online and they don't have any, just the fuse diagrams". :(
Thank you in advance to help my Simple problem". :)