I'm guessing the "guide" just pops off when the top of the bar starts to enter the cut, or the user could just pull it off when he has his mark. To me, it would be easier to have a piece of wood cut to the length you want, and just sit it on top of the log when you start your cut. Regarding the electric saw, I've used one or two that were certainly more than powerful enough for non-professional work. If that's a 40V or 80V battery powered saw, I would probably go for quite a while, too. Unless I was doing a lot of cutting out in the middle of nowhere, I don't think I'd ever buy another temperamental 2-cycle saw, again. My 18V battery powered pole saw will cut through an eight-inch branch like it's butter, and all I have to do is pull the trigger and add some chain oil every now and then.