You've seen your friends get their ponies and horses to step over sideways to get a jacket off the fence or the mail from the mailbox. When you try to do it, your horse just goes forward or swings his hind end way around and you can't reach your target. Your friends can even open and close gates while on their horses. "How do you do that?" you ask, and they probably just say, "It's easy. You just use leg pressure to signal him over." But when you try that, your horse doesn't do it.
That's because he hasn't been taught to yield sideways away from pressure. He may know how to go forward from pressure, but that does not mean he will know how to go sideways. So how can you teach your horse to yield sideways? It's easy - you just use common sense - horse sense.
The horse knows how to step sideways because he does it all the time on his own. What he doesn't know is that you want him to do it when you request it by applying leg pressure to his side. A horse does not naturally move away from pressure; he leans into it instead. That is a normal reaction for an untaught horse. What you must do is teach him to yield to pressure, meaning to move away from it rather than into it. To do that you need time, patience, a halter, a lead rope, and a friend or adult to help you if anything gets difficult. You must teach him on the ground first, and then you can transfer that over to riding.
CAUTION: There are always some risks involved in horse training for both you and your horse. If your horse is likely to kick you or disrespect you, or if you don't feel comfortable with your horse, let an expert do the training. There are different ways to teach horses and this may not be the best way for your situation. You know your horse; use your best judgment.
With the lead rope in your left hand, face the horse's left (near) side, standing almost an arm's length away. With your right hand in a fist, slowly but firmly press into his flank. At the same time, with your left hand, take the slack out of the lead rope so his nose turns slightly toward you but his front feet don't step toward you. (You can block his front feet from stepping toward you by pressing your rope hand into his shoulder if needed.) He may at first step his hind end toward you or lean into your pressure, and if he does you must keep your hand steady and firm,
then he will try to get your hand out of his flank by moving his hindquarters away. Give him a nice, stroking pet and tell him he's a good boy!
Normally the hind leg nearest you will step over first, crossing in front of the other hind leg. If he steps away sideways with his hind legs, be still and let him move away from your hand, then quickly put your hand down by your side. When he does, he rewards himself by stepping away from your pressure. Pet him too.
If your horse steps forward rather than sideways,
keep pressure on the lead rope and on his flank until one hind foot steps over off its path, then immediately release the hand pressure. If his front feet stop, release the rope pressure too. You want him to learn that going sideways is what you want and not forward, but you need to reward one thing at a time if you get only one thing at a time. So you first will reward the step over if that happens first. If you release your hand pressure when he steps only forward, he will think he did the right thing because doing the right thing is rewarded by the release of pressure. Do not confuse him by giving him a release of pressure for the wrong thing! Wait until he steps over and then release your hand pressure.
If he is stepping over and continuing to walk, keep the rope taut and let him continue walking in a circle around you (not into you) until he stops his front feet, then immediately release the rope pressure and pet him. If your horse walked only a few steps forward, and if he knows how to back up well, back him up the few steps to where you started and pet him there, just to give him the message that you want him (his front legs) to stay in that place. Then try again.
If your horse walks backward rather than stepping over, walk back with him, keeping the hand pressure on his flank until one hind foot steps over, then immediately release the pressure.
If your horse seems dull to the pressure, you can open your hand slightly and press your knuckles into him, or use your thumb, so he can feel it better. This gives your hand a sharper feel and a more definite signal to him to move away if needed. This is usually only needed the first few times during the teaching if your releases are immediate. Repeat this until he responds quickly and willingly to the slightest pressure, and reward him each time he does.
Then go to the horse's right (off) side and teach him on that side.
Reward all his efforts and practice until he does this well.
Next you will do almost the same thing, but your hand holding the lead rope (and taking out the slack) will press on his side, his ribs, slightly behind where your leg would hang when you are riding. At the same time, your other hand will press on his flank.
Hold the pressure until he steps over with his hindquarters, then release both hands. Practice this until he does it well, then try moving him over with just pressure on his side and not the flank. At first use the rope hand to signal him in the ribs so that your other hand can 'remind' him on the flank if he doesn't respond. Once he understands, you can use either hand to signal his ribs.
What you are doing is transferring the "over" signal to where you will use it with your legs when you are mounted. The horse's ribs are not the best place to start teaching him to step over, but the flank is. So the flank is where you must start, and once he understands the concept you can move the signal forward to his ribs to imitate a leg signal. Remember to lower your arms as part of his reward as soon as one leg steps over away from your signal, and to pet him.
Once he steps over with his hindquarters willingly and quickly from the signal on one side, teach him on the other side. Move him to a different place and try out your signals there, and then try it somewhere else, perhaps at the mailbox. This is to make sure he learns that this lesson applies no matter where you are. With horses, sometimes little changes turn it into a whole new lesson. This is why teaching horses on the ground first is so important - it is a foundation on which you build all other lessons. Most lessons are easier for the horse to learn while you are on the ground with him than while riding him.
Once he knows this rib signal well and does it willingly anywhere, the lesson is almost over and he can be bridled. Slowly take the slack out of the rein (the one closest to you, on the same side that you are giving the rib signal) as you did with the lead rope, keeping lots of slack in the opposite rein, and signal him with your hand in his ribs to step his hindquarters over. Remember that being bridled, saddled, or mounted may change this into a whole new lesson, so be understanding. You want him to step over from your rib signal with the bridle, saddle, or rider on as readily as he did without them, and without going forward or backward. If he walks forward, don't release your rib signal until he steps a hind leg over, and don't release your rein signal (one rein, not both) until his front feet stop, just like you did when you taught him with just the lead rope. Don't try to pull on the slack rein or both reins to try to stop him from walking. Reward him with nice, stroking pets. Practice this from both sides until he does it well.
Now get your saddle and saddle him, but don't mount him yet - first signal him to step over with just the saddle and bridle on, without your weight. Use your hand in his ribs at that same spot, slightly behind where your leg hangs when you're mounted. Be sure he responds well from both sides, and without walking forward, before you mount him. If he is doing this well, you can finally mount him. Get your helmet!
While mounted, slowly take the slack out of the rein on the side where you are signaling with your leg and let the other rein have plenty of slack. Signal him in the ribs with your leg, slightly behind where it normally hangs, to step his hindquarters over. This may take a few tries because your leg pressure gives him a different feel. Keep the leg pressure on until he steps over, then release your leg pressure immediately. Do this on both sides.
Again, if he walks forward, don't release your leg signal until he steps a hind leg over, and don't release the rein until he stops his front feet, just like you did when you taught him on the ground. Don't pull on the slack rein or both reins to stop him from walking. If he does not understand your leg and rein signals, dismount and use your rib and rein signals on the same side, then immediately remount and try again. Be sure that you have a loose rein on the side opposite your leg signal. If he does not catch on after a few tries, ask your friend to help him understand by giving him the hand signal on the flank while you give him the leg and rein signal. He will surely understand what you want then. Make sure you both release the pressure as soon as he steps over! Give him lots of stroking pets.
When he knows what you want and responds willingly and quickly, move to another spot, and then another - like the mailbox!