As Hugh says... friction....and I put a little beeswax on the pin... it will be behind your lockplate on one side and it may or may not go all the way through to come out the sideplate side..or even be hidden behind the sideplate ..depending on the sideplate... I like to bend the end over to make a small L on the lockplate side and not drill quite all the way through the sideplate side.... that way I can take the lock out, grab the pin with a pair of needlenose pliers and remove it when I want to remove the trigger.... Not sure if they were ever done that way on originals, but it works for me.