My brother's looking to do something to the transmission on his scooter (I didn't ask and I don't want to know.)
Anyway, there's a tool that stops an assembly from rotating whilst you undo the centre nut, it can be seen in panels 1b and 2 of the following PDF:
I know what it's for and I expect that a couple of ring spanners tied together would do the same job but assuming that I have to go to a bike shop and buy/borrow one in front of half a dozen hairy bikers, what would I have to ask for to avoid being laughed out of the place?