I needed a battery box for 3 AA batteries for a 3.3V micro processor project. Uses #6 nuts and has holes for 1/4" #6 bolts. The holes are not need but are there if you need to use them for the bolts. The batteries will have a tight fit, but after you insert the batteries a few times, it will push the nuts into the holes. I found that the bolts were not needed at all after I had printed it, but makes for a clean wire connection. Also, if you can get away without using the bolts, you will not have exposed battery contacts to the outside of the box.1) Print the battery box. 2) Use a piece of wire or copper tape to link the middle battery to the outside battery. See pic, do the same for opposite end. I used copper tape in picture. Cram the tape into the nut hole before inserting the nut. 3) Insert wire into 3rd hole from the back side. Strip off enough wire to get a good contact to backside of nut. 4) Press the in the nuts with pliers. It is a tight fit, but they will go in, trust me. A tight fit is better anyway. The nuts will make contact with the tape and wire. You can insert some glue into the wire hole for added stress relief if you need it. 5) Insert 3 AA batteries as shown in picture. 6) Enjoy.