Thread: jointer blade hone question

I've bought this diamond hone for my jointer knives:
http://www.carbatec.com.au/sharpening-tools/blade-hones

but I can't work out how to use it
The fine diamond hone, the one set at 45º, I can see sits nicely on the bevel of the knife but I don't understand how the course diamond hone is to be used. In the picture it looks like it does the back of the knife, but I don't seem to be able to get it to sit flat on the back face.

Anybody know how to work these?
okeydokey, I had a bit more of a play last night and worked out that the 45º one (fine) does the bevel and the square set one (coarse) does the bottom, but I can't work out why they are two different grades? I expected you would be able to do course followed by fine grade on both faces.

Cheers
Michael