My Bosch does not have one, so I bought one and use it for cuts that only need to be within a 16th or so close. It works pretty well, but sometimes it doesn't turn on, so I need to restart the saw. The real problem is that the saw needs to be running for it to work. Not so safe to run it just for alignment. But so far, I have most of my fingers! All in all, I'm glad it is on the saw. Sure wish it came standard!