/diy/ - Do It Yourself

why do guys using rear handle saws put their left/front hand on the front of the shoe? it seems like it is a pretty sketchy thing to do.
I assume its to help stay on your cut line but I'm hourly so id rather just clamp on a guide. I have regular circ saws and table saws but picked one up as a promo to get a free 6amp battery yesterday and was dmor on the thing since I don't remember using one before.
here is a review vid with lots of examples of the technique in question:
skip to 1:30 if you don't want the intro
>https://yewtu.be/1-0mZsozaiE
also any tips and horror stories would be apreciated.