I have a couple of sets of eye brow stencils. I like to use them when I can't get in to a town for threading.
I was sent a set of Legends stencils by Miss Bollywood which are available from their website for £10. The kit is fairly straightforward to use, the only thing requiring any skill is to pick the shape of brow and place the stencil in the right place.
I have found these incredibly useful as I always have one eye brow which isn't the same shape as my favourite brow. I also used these on my sister the other day, following the instructions in my video below. She was a bit hesistant but I assured her that they would grow back! For years she's had neat eyebrows but they weren't a natural shape and she just looked a little surprised most of the time as they were too lifted at the tails. We've all done that with our eyebrows, I am trying to grow the tails of mine so they point downward following my browbone. My eyebrows are quite sparse due to hair loss but grow long so filling them in keeps them looking neat and shapely.
It was really easy to use the kit on myself and even easier to use on my sister. I have to say trimming her "virgin - never been trimmed" eyebrows was really satisfying! The results were very good, but she needs a little time to get used to the new shape and they need to regrow to follow the shape of her brow, just like mine.
So I'd recommend this kit or any stencil kit as long as you're happy with the brow shape they give you.
See my video below for a demonstration.