If you are replacing the power & sensor cable with a new unit, use the edge of a plastic opening tool to peel the electronic power switch off its metal bracket.
Also be sure to transfer the proximity sensor foam/UV-filter adhered to the old power & sensor cable if your new one does not already come with one. It looks like a small square and can be peeled off with tweezers.
Transfer the bracket to your new power & sensor cable.
Now this is more helpful, than the power button repair guide that they gave us. This one still kind of leaves me hanging on how I'm supposed to put the silver button back into the hole so that it makes contact with the orange dome(aka the powerbutton).
I replaced the Home button and the Power & Sensor cable, along with battery. Let me explain some caveats with ifixit's parts (OEM Apple parts):
-The power-sensor part does not include a new gasket/filter for the sensor- recommend tweezers and care.
-The power-sensor cable needs the foam pad transferred with the adhesive- extreme care with removal.
-IF the power button isn't working it is likely the cable, not the button.
-I used a small ice cube tray.
-It took me an hour (I had to get up and walk away...frustration factor high with the delicate flex cables and adhesive). Lit magnifier is welcome. Definitely use a spudge stick.
-I broke 2 of the 4 shield/antenna tabs that you need to tuck down from the speaker on re-assembly. I didn't force them, but so easy to press too hard in seating the speaker.
- I do repairs on a grounded-ESD mat and wore wriststrap.
-Right screw on the power button brace is PITA to access...careful pressing on the display flex cables to access the tiny screw. Magnetize your bit!