There is such a thing as a snatch block...I've got one.
And its seen a lot of use over the years.
It's a pulley between two steel plates. The plates are folded in such a way that they meet together at the top and have a quite large hole through them that can take a heavy chain (or shackle) through it.
They're used for snigging logs through bush.
If you can't (or don't want to,) get a straight pull on the log you're snigging, you attach the snatch block to a suitable anchor-point with a chain or strop and run the snigging rope through it.
The snatch block plates are attached together only at the pulley so that they can be opened from the top, the wire snigging rope placed inside, the plates closed and held closed by the anchoring chain to form a normal pulley.
Dead simple to use.

They're a very handy thing to have when working in the bush. ('Woods' to you Americans.)