as bruce said the pin you are crimping should be held in the tool,you may have to spread the ears a bit to add more spring tension so the pin will stay in the too while you close it to keep the pin in the jaws then add the wire then crimp.they work really well,I used them to change out the spring type battery contacts on my 7ua transmitters so they can use the same battery as the 8u.also to change g connectors to j connecters.