You can splice barbed wire with a hammer by using a special tool designed for the purpose. The tool has a blunt end that you use to insert the wire into the slot on the top of the tool, then you use the hammer to hit the top of the tool and drive the wire in. This will create a splice that is strong and durable.

There are a few ways to do it. One way is to put the wire into a vise and then use the hammer to hit the barbs of the old wire so they will puncture the new wire. Another way is to use pliers to hold the wires together and then hit them with the hammer.