If we put the key on fixture in normal way,a part of the tooth view will be blocked.
We suggest you to swtich the clamp 180 degree then insert it,then fasten the clamp.
As some key blades are not standard one,it can not be stable if put on the clamp,we take the front-end postioning, clip to the root.
Put the new key blade on left clamp,then fasten it.
Then we check the height.
Start to cut.
If the back side of the fixture is difficult to clamp or hard to fit the key blade,you can swtich the clamp like this blog to try.