I have seen people put up a vertical that consists of a metal pole, with coffee cans (with the tops and bottoms cut out) around it. So if they touch the pole it makes a loud noise and scares them. You have to be cautious with this, but it can be useful
Will try to explain this as best I can..
Start with an upright, a ground pole and a canter pole 3 paces out - trot until your horse reaches the canter pole then let him canter over the fence. This teaches them not to rush also and snap up.
Another one being a simple upright or oxer with A-frame poles either on the ground or on the front pole aiming towards the middle of the pole. Hope these make sense 👍🏼