Anyone know how to bend / cut those plastic electrical casing...like bend 90 deg etc. Being searching on net/youtube cannot find.

Thanks

I assume you are talking about those used for encasing the fiber optic cable, white plastic strip type. They cannot be bend to 90 degree. For the bottom stip that's nail to the wall, just cut them and place them at 90degree. For the top cover, to make it look nice, cut them at 45 degree and when you place them together, you get a nice joint. How nice depends on your skill. To cut them, use a small saw. The professional just use a wire cutter but they are skilled.