Jumping can be great fun for both horse and rider, and, as jumping correctly encourages the horse to use its topline, can be seen as a valuable training tool, even for riders who aim to improve their dressage!
The success of the jump depends almost entirely on the correctness of the approach. When linking fences together to make a course, the get-away from one fence becomes the approach to the next, so in this exercise we focus on introducing a jump in such a way that we can easily progress to more complex options. (When coaching, I might variously use this exercise to introduce jumping to novice riders or horses, or to build confidence through predictable, repeatable take-off points, or as a springboard to creating a grid for gymnastic jumping).
1) Place 3 heavy poles about 5 meters in from the wall at either E or B. The poles should be about 1.35 meters apart for a horse of 15.2hh or over, about one and a half normal human strides. You can make them a little closer (about 1.1m) for ponies.
2) Ride in an active trot around the arena. Turn down the line towards the poles and maintain your rising as you go over them. Focus on riding as straight a line away as you did on the approach, and ride all the way to the end of the arena before making a balanced turn. Try really hard not to let the horse fall on his inside shoulder and cut the corner after the poles - teach him to always move away from an obstacle straight and in balance and he’ll soon take ownership of that, making your life much easier!
3) When your horse is trotting rhythmically over the poles and moving straight on landing you need to get your jumping muscles warmed up! As he trots over the poles, start to balance in your light seat/2-point seat/jumping position/on your leg - whichever expression you prefer. To do this, have your stirrups 2 or 3 holes shorter than your flatwork length and fold at the hips whilst taking more weight onto your stirrup so that your backside is just hovering out of the saddle and your shoulders have come slightly - just slightly - forwards. Move your hands up your horse’s neck as you do so so that the rein is allowing - it can really help to hold a bit of mane about halfway up his neck to start with. Keep your head and your eyes up and look at the end of the arena, not down at the poles.
The GIF is just for fun! You're doing your light seat in trot. And with your heels down, unlike this guy!
4) When you can do this easily it's time to build a small jump where the last trotting pole is (red x-pole on diagram). Use the last and the middle pole to create a cross pole as high as you are comfortable with - about 65cm at the sides is usually about right. The first trot pole should now be about 2.7m, or three human strides away from the jump. Leave it there - it is now your placing pole, which will help make the take-off point for the jump predictable.
5) Ride positively towards the obstacle in trot, exactly as you have done on all previous occasions. At the placing pole close your legs, and let the horse move over the pole in trot or canter as he wishes. He is now in the perfect place to take off over the jump, fold and go with him. He will probably land in canter, make sure you ride to the end of the arena and make a balanced turn. Don't worry too much about canter leads at this point - you can make a change of leg through trot on the turn at the end if you are organised enough - but for now riding away straight is the most important thing.
6) Return to trot on the long side of the arena, rebalance and have another go! You can increase the height of the cross pole but don’t put the ends higher than about 1m as that will make the angle of the X too steep for horses and riders starting out.
7) If this is all going swimmingly and you’re keen to do more, then add a pole on the ground about 6.5m from the cross pole (marked blue on diagram). Your horse needs to land from the cross pole, take one canter stride, then jump over the pole (shorten the distance a little if he's taking one and a half strides and the cross pole is very small). When he's doing this happily you can make the pole into an upright fence of about 60cm. Don't make another cross pole - it may feel more inviting, but if you fail to stay dead straight you'll end up jumping a high side! Remember to keep riding away straight and making a balanced turn.
I would suggest that it is possible to do this exercise in a 20m x 40m arena, providing you can make smooth balanced turns at either end, but a slightly larger space might be easier if you need more time and space to organise yourself. In a larger space you could also carry on to build a grid, adding a third fence about 7m from the second.
Also, please enlist the help of someone on the ground. Even if they are non-horsey and you have to get off to walk all the distances and set the exercise up, it is always safer to jump with someone else at hand!