This cutter is great for cutting right through the bottom of the J Channel, but if you want to make a curved tongue it's not very good. I used it at work last week and the temp was at 70 but the cutter still broke the J channel on some cuts and in most cases it was possible to make a curved edge but not with any Consistency. To make a 45 degree incision on the face, use metal scissors. I couldn't get the j channel face into the cutter. This saves time when cropping windows, but not as well as shown in the video. Maybe it's because I used it on a cheaper Royal Crest siding? I don't know, but here are the results I got using this tool.