I had a significant nick in both jointer knives, and I was in the
middle of a project and on a Sunday--couldn't get anything sharpened.

I use the "Scary Sharp" system of sandpaper sharpening with a veritas
jig, but the jig wouldn't fit the jointer knives.

I was able to orient the beveled edge of the knife on the glass by
rocking it until I was sure it was the right angle, then I could
maintain the sharpening angle by hand. It took me about an hour
working through the grit sequence, but I was able to restore a perfect
edge.

Of course a jig would give you more security and be "fool-proof."

Mr. Fixit eh.