As stated in a previous post I made the butt strap (which joins the two halves of the cabin roof together) too long.
It should stop 2 1/2" short of the forward cabin wall, to give the companionway front face some clear deck to land on. For some reason I continued it all the way to the cabin wall.
No matter. Some careful work with a chisel would remove it.
So I cut through the strap with a tenon saw, taking care not to cut into the deck.
Then I chiselled and pared the excess strap away, leaving clear deck.
This is what it looked like afterwards.