This is when people wrap a horses neck to remove the water and make the horse sweat so the neck looks smaller and more shapely. Here is how a person sweats their horses neck.
First you want to have brushed off your horse and make sure there aren't any shavings, dirt, etc where you will be placing the sweats.
Next start with a 10" wide throatlatch sweat, when putting on the sweats be sure to lay them down in the direction of the mane. This will help the mane lay down, and not make it stand up. For instance her mane is on the left so I put the throatlatch on her and then pull the top down in the direction of the mane. This one doesnt need to be super tight, just snug
Then put on a 6" throatlatch overtop, this one you want to be really tight, so pull it really taughnt then velcro.
Then overtop of that add a regular size neck sweat
Next you can either add another regular size neck sweat, or if you want them to sweat more add a blue sauna sweat. If you're just starting out sweating a horse I recommend starting with just the two regulars and after the horse has started getting more fit then add the sauna sweat.
After the sauna sweat comes another regular sweat(there is only one regular sweat underneath the sauna sweat, not two, only use two regular sweats if not using the sauna sweat)
Once the horse has its sweats on we lunge them for 10 min, 5 min each direction. Then they stand tied in their stall for 1-2 hrs or until they are done sweating and start to cool off. You can ride a horse with sweats on, but the sweats have a tendency to move more.
About a month before the horse is going to be shown we also add a fleece throatlatch that they wear during the night and have taken off in the morning.