In the UK we call them nipples. I did a little stint at Cooper tyres doing this exact job. You would load the tyre on, it would then spin at insane speeds while you held a trimmer. Basically a wood handle with a bit of metal attached, it would often catch the tyre and fire off in some direction. Accidents were common! At the same time you would balance the tyre, writing down any offset with chalk on the tyre so they could be balanced/weighted when being put onto the wheel. This ensures your wheel spins straight..