This is a very rugged C cell battery holder that can stack modularly. The C cells snap in (push real hard). The battery holders can be stacked together and even glued to make 3v, 6v, 9v, 12v, 18v, etc. C cells provide enough power for almost any job. There is a grove and two holes on the side for a twist wire for further securing either the batteries or the holder. To remove the C cells there is a hole in the bottom where they can be pushed out. Have fun. I drilled and tapped the holes in the ends for 10-32 brass machine screws but there is sufficient room for a nut on the inside if you decide to drill through. By using brass machine screws for contacts you can get a very strong connection that is very reliable.