This ½” to 10mm adaptor is used when you have a ½” male fixing and want to fit a 10mm fitting or lampholder. The adaptor has female threads both ends and one being ½” and the other 10mm.
To fit a 10mm lampholder, add the adaptor to the ½” male thread then add a short piece of 10mm allthread to the adaptor. Add the 10mm lampholder to the Allthread to finish the fitting.