Slide the tab over the end of the end of the 2.5mm connector and make sure it fits tight. when you apply pressure to the top of the tab with your thumb, it completes the circuit and commands the shutter operation. I can comfirm this works with my Canon T4i(650D). A better way to do this would be to cut off one of the 2.5mm cable ends and attach a momentary switch to the open connections. With heatshrink tubing and a store bought switch, the switch could look clean and professional, however, this instructable was made to show how i used the resources around me to rig together a make shift switch as an emergency.