At Advanced Level, the obstacle says "Mark a corridor on the ground using poles, tape, rope etc which is 5m long and 5m wide. Arrange five markers up the centre evenly spaced, this should give you a little over 1m between each marker. The horse follows the track marked at trot. Horse must not cross outside the corridor. Handler does not weave but follows path marked red." (along the outside of one of the poles, see diagram).
In order to be able to cause the horse to weave, especially through such tight turns, whilst you are 2.5m away from the horse (and, if online, add the weight and the movement of the rope into the equation as well), you really need to have good, clear, body language communication established with your horse. The key is in breaking the task down into smaller components and working on those individually, then putting it all together. As so often, there is more than one way to approach this, the way that I prefer is to work on 3 components: 1. being able to send the front end of the horse away from you. Meaning, being able to point his nose away from you and have his body following his nose. 2. being able to drive the back end. The nose is (hopefully) heading in the correct direction, with the body lined up behind the nose. Now you need to engage rear wheel drive in order to keep pushing the nose forward in the original direction of travel. 3. draw the front end back towards you! The nose has now gone far enough (through the cones, in this obstacle) and you don't want your horse to just keep going, you now need the nose to turn and come back towards you (through the next gap in the cones), bringing the body along with it. I work on those 3 components quite slowly and pausing between each one, in order that the horse is clear about what I'm asking (or, more usually, to allow me to train my body to accurately work at the speed the horse's brain is already working at, lol!). I also start very close to the horse. As s/he gets the idea, I start to work from further away and, once that is established, I speed it up until we have a smooth movement through the whole obstacle.
I've really enjoyed working on this obstacle! It actually wasn't as difficult as I thought it would be and it turned out to be a fantastic schooling and suppling exercise, as well as really testing communication. We haven't got it all the way up to trot yet, but solid in walk and a few jog steps mixed in. A bit more practice and I think we'll have cracked it :-)