For example you could buy puts, sell calls (aka a risk reversal) and bet on the call touch. When the underlying gets there and you have a profit you can either close the position or fly it off with buying wings for the same vols you originally sold the calls for which gives you a nice bet on vega and wing vol.
On the other hand it could just be a vertical that you flattened with regards to delta and turn it into a fly by purchasing wings.
Or you just made a bet with two strikes in an illiquid chain. Most of the time it's easier to just buy or sell a single strike and turn the position into a fly opposed to just liquidate at the market.
You could also be long stock, sell two call verticals against it and buy a put to make some dosh in a range without capping your upside.
Synthetics are everything