I certainly could be wrong as I have not examined the tool itself but I got the impression, from the diagrams I've seen. that an adapter is secured to the shaft of a slide hammer. After the injector and the prechamber's retaining ring have been removed the adapter piece is threaded into the prechamber in place of the injector. The slide hammer is then used to slap the prechamber up and out from its' recess in the head. The reverse action could be carefully applied to put prechambesr into their respective head recesses also. Although with a new head, clean recesses, and prechambers you may be able to just drop them in. It does not appear that there would be any other contact with the head itself. But I'll be happy to learn anything as I'm anticipating possibly having to do this procedure.