Why do so many modellers fit the scuttles/portholes the wrong way around?
Manufacturers of modelling items compound the error.
With a few exceptions (some fishing boats and "Gin Palaces") the flange is on the INSIDE of the bulkhead it is attached to.
There is a good reason for this which I shall come to soon.
From the outside all that can be seen is a very thin (perhaps 1/8") rim protruding about 1/4" outwards, surrounded by the usual 8 round-headed bolts. (After reading the "only for Engineers" topic I am wary about this...and how do you hold the "round" head when tightening up the nut?...)
The inner flange is a quite complicated casting. First, it has to hold and secure an opening "window" that in itself has to have a wterproof seal and fastening flanges. This is held on a cast bracket on the inside of the main flange. You may well find a "deadlight" also held by the same bracket. It should be obvious by now that all of this stuff cannot be fastened on the "outside". (The glass alone will be over 1/2" thick and has to be removable...more threaded castings.
To a modeller, scuttles may well look like simple things....but they ain't. Also, they have to be big enough for a person of (a bit over) average build. There are at least 20 "bits" that go into each scuttle...and they are heavy. Please put them on the correct way around! BY.