My friend has a race system with a catching gate at the end. The race is as wide as a large fearings pig board so you can move the pigs along it. The gate at the end has a hurdle attached about half way along it. The race runs along a building wall.
The hurdle is attached to the gate so it swings. So when you open the gate the hurdle stays to the side and doesn't impede stock movement but also you can close it against the wall in the other direction making a crush you can catch the pig in. the hurdle is attached to the wall with a chain and clip so you can put any size pig in it.
You can have any number of pigs in the race. Catch them up. Inject, tag or whatever and let them out. The pig scales fit on the other side of the gate so you can run them through and weigh.
Hope that makes sense.