DIY Round Windows (old ship building technique)

My Google-foo is failing me...
I've seen somewhere on here in the past... someone built some really good (and simple) ROUND porthole style windows that open/close from the inside, with a wedge if I recall correctly...
If my memory serves me correctly... the technique was borrowed from old wooden ship building...
Any chance anyone remember what these were called? Perhaps a link?
Thanks in advance!

I've seen somewhere on here in the past... someone built some really good (and simple) ROUND porthole style windows that open/close from the inside, with a wedge if I recall correctly...
If my memory serves me correctly... the technique was borrowed from old wooden ship building...
Any chance anyone remember what these were called? Perhaps a link?
Thanks in advance!