Think Once, Cut Thrice

In my professional life I've always taught myself to 'think thrice, measure twice and cut once'. That's all well and good in theory, until it comes to the subject of boat interior renovation.

I just can't believe what a plonker I was when I got to the bit where I repaired the 'ceiling' in the 'bedroom'. On discovering the existing wood was so dilapidated, I decided that replacement was the only option.

I thought about it three times, accurately measured it twice and cut some lovely new plywood just the once. Proud of my handiwork, I fixed the timber into place, and stood back to admire my work.

I continued with the job by fixing two struts and all new trim using screws and glue, as well as I possibly could do.

'Right', I thought to myself. 'That ain't going nowhere'. As I looked around for the celebratory bottle of beer I'd brought along for the occasion, my eyes caught sight of the air-vents that I'd put aside and that I'd forgotten to cut the holes for.

I've now got to work out how to accurately cut said holes in exactly the correct position to line up with the top halves of the vents situated on the deck. Unfortunately, I can't remove the tops and mark the positions from above.

Any suggestions?

Oops. If only I'd thought about it four times instead of three.