Measure twice...

...cut once, so they say. Or in my case measure about four times, cut and still find you've cut it wrong!
So today's task filled me with understandable trepidation. Cutting the holes in the cabinside panels for the portholes. You think it's easy, eh?
First comes the task of getting the eight feet long panel lined up square on the cabin side - remembering that the side slopes inwards so gravity is your implacable enemy in this job. If you don't get it square then subsequent panels will only amplify your seemingly tiny error. A Workmate and a carefully arranged pile of scrap timber at least supported the base and gave me a fighting chance.
And once you have got the panel up you can't see the portholes any more so the position of the holes has be gauged by accurate - very accurate - measuring. Which is made harder because you've just taken the panel down and have to rely on a variety of pencil marks and a string line to recall where it was.
Understandably I cut a very small hole to begin with. At least I could see glass through it and not sprayfoam! Next came a rather bigger hole (still well within the eight inch diameter of the porthole). And, yes, the glass was still underneath.
Next I trimmed my best (best because it was my only) pencil down to a stub, put my hand through the hole and attempted to mark the circumference of the porthole on the back of the ply. The result when I removed the ply looked like a drunk's attempt to draw round a large beermat.
But there was no more prevaricating. It was time to cut. I worked the jigsaw round what looked the clearest approximation to a circle, repeated the job with the other window and hefted the ply up yet again. Unbelievably the holes were in the right places. Even more unbelievably the porthole liners fitted into them. Well, with a little bit of skimming here and there they did.
Job done.
One panel up. I retired to soothe my frayed nerves and aching tennis elbow with a beer. Only six more window holes to cut.