If you google "pelletgage" you will find images and videos of it in use, the maker has a website as well http://pelletgage.com
Having said that it is only measuring the head size, the skirt is retained in the outer plastic template which sits on top of the thin stainless steel plate with the holes in. At around £50 delivered they are not cheap at all but I think they are a necessary tool to be used in pursuit of consistency. Only had it a week and not tried loads of pellets through it but it could be the holy grail. Time and persistence will tell.
I have read an article where somebody tested the match grade flatheads and I recall they were very consistent on head size.