diff backlash and adjusting?

good day, just wondering how do you check the backlash in the diff and how to adjust it?

from memory its about 4 to 7 thou. normally adjust with the replaceable collapsable sleeve that fits behind big nut on the main shaft. cant for the life of me remembeer what the fook its called, but its a sort of a lead wire the u put between the teeth of the diff and adjust the sleeve until u get yer measurement right