i follow exactly what the tutorial said, but how come my screwdriver like this?
https://micah.noobgrinder.com/screwdrivertut/

this is my screwdriver model


this is before render


since i don't have what he called, HDRI map, so i didn't fill that part. i render and after that, i got black map , i use alpha channel to see. and i see one white screwdriver


is the HDRI map really so important?