I have some guys adding a ridge vent to my house (not new
construction).

Of course, they stripped off the old shingles at the ridge and cut
through the wood to make the vent. When they added the ridge vent
system, I don't think there were shingles covering all the wood
underneath the vent - you know, all the way up the roof to the vent
hole. There was some exposed wood underneath the new ridge vent - not
much, mind you; but the pictures of ridge vents that I've seen show
shingles all the way to the hole.

Is it common practice when installing a vent to leave some exposed
wood, or should these guys replace the shingles up to the vent hole
before covering with the vent hood?

Thanks for your help!
squanklin at yahoo dot com