Actually that is not Rubylith but I can see how Peter made that mistake. It is actually indirect emulsion. It's a gelatinous sheet that gets exposed the same way diret emulsion is exposed then it is adhered to the screen. The benefit of indirect emulsion is that you get sharper details and a thicker emulsion. The downside is that it can be a pain to use.
Sorry SQEE3, that stuff in the link is actually Capillary film, which is adhered to a screen, dried and then exposed. (A bit different than Indirect.) It's benefits are controllable thickness and great detail. It's capillary action, where it bonds itself to the screen mesh, is the big advance over INDIRECT FILM, the stuff shown in the video. Funny, if it is what we used to use, from Autotype, it's called 5-star. (Hi 5, get it) Ulano used to make Hi Fi green, same idea. Autotype had a range, 5-star, Nova star - no idea if they still make indirect films.
It differs from the CDF Cap film in that after cutting it from a roll, you expose it with your film and light, dip it in a mild peroxide solution, and then wash it out. Once washed out, you stick it on a screen, then dry it. If you did it right, you peel the clear backing off and your screen is ready to go.
It's biggest drawbacks, and I know these from using it for years, is (a) pain to do big stuff, because you have to tray develop, (b) it doesn't bond as good to the screen as the cap film, and nowhere near as tough as direct emulsion, (c) is hard to clean clogs or blockage without damaging it in production (d) expensive, and for posterpeople, it doesn't work worth shit with waterbase inks - this is also a problem with the Cap film.
It's advantage is really good detail, and quick - while you are burning your stencil you can reclaim a screen. Once washed out, stick it on the wet screen and put it on a fan. You can be printing in about 20-30 minutes.
direct emulsion is way cheaper, can provide the detail if done properly, and way stronger on press/cleaning. It is also water resistant, which makes it handy for us who use waterbase inks.
Well I couldn't find a link to indirect in the first 3 google posts so I posted that instead. Same general concept. I've only used indirect a few times and while it was fun to use for a change, I doubt I'll use it again for the reason Andy states.