The ones I have (and like very much) are quite like these ones
https://canada.newark.com/hirschmann...be/dp/06WX5804
The Hirschmann ones extend two little hooks which open and close as you pull or release the finger guard. Mine look so similar but open a little anvil opposite a fine pointed contact which will penetrate insulation. Mine ( I've owned them some years) are branded "Texas" and I cannot now find anything about them on the internet.
B