or you can pull up fm23-8 , page 26- that tells you HOW it works- if you get the large technical manual it's got "drawings " - basically, there's two components- first you have to have a REAL m14 trigger group- there is a difference- hint- it's ON the hammer- the early norcs have this , but the later ones do not- and then there's a bunch of stuff( look at your parts list) on the receiver that engage the trigger group- when these two mate, you get severe depression and she goes select fire- basically it has to do with holding the hammer hooks back