Photo-etch

Photo-etch (or "PE" for ease of typing) parts are small frames with tiny little parts made from metal. The term "photo-etch" refers to the process that makes these frames, but no need to go into detail about that. They are generally used to create extremely small or thin parts, which would be too delicate in plastic - or simply impossible to make.
You often find PE parts in aftermarket kits to add superdetails to existing models : railings, grab handles, antenna's, ... which aren't always in scale when made in plastic.

I intended to experiment with PE later in my "modelling career", but was surprised to find a small photo-etch frame in the submarine kit. It consists of the propeller, some antenna-blades and the nameplate for the display stand.

The PE version of the propellor is optional, since the kit contains a plastic version. (seen below, the rightmost part), but I want to grab this chance to work with it for the first time. It would be a waste not to try it.

The building instructions tell you to cut off the plastic propellor, but best to wait with that until you've successfully removed the PE one and folded it into shape.
This is one of the things about PE : you have to fold them into the right shape. Not all parts, but more often than not, folding is necessary and you need to do this really carefully. (special tools can be found for it)

The PE frame is usually packed in (self-adhesive) plastic. Do not remove this! It will help you when cutting off the part, to prevent it from flying off your desk onto the floor, where it will be eaten by the carpet monster. (Tip: keep your workbench away from carpet, if possible)
Cut through the plastic wrapping to remove the part. Use a sharp hobby knife and avoid using sprue cutters, as these are not intended for cutting metal.

I removed the propellor, peeled off the protecting plastic and  gently bent the propellor blades. It's extremely thin, but feels stronger than I had feared. Handle with extreme care though.

(Sorry for the picture quality, I seem unable to get my camera to focus on small parts)

Below you see the part in it's place, inside the propellor housing. It's still missing it's cap, since I decided to play safe and not remove the propellor blades until the PE one was in place. The cap is now painted black and drying. Although the plastic one, once painted gold, would probably have looked okay, the PE result will always look extra sharp.