Handy tool to carry in the service truck back before we carried rolls of Manheim belting.
Just cut the end of the belt square, find a place to clamp or screw the block down to, and see if you can force the cutter into the end of the belt without loosing a finger. Then you "slip" one half of the coupler in, insert screws, and do the other end. It helps a lot if you remember there are A and B halves to the coupling, and have a magnet on a stick to pick up the pin that holds the deal together when you drop it 7 times because you're tired.
They don't work worth a dam going around pulleys smaller than 2" and definitely are worthless on belts that have back side idlers. Works well on both A and B belts.