First things first! Your safety is number one! Repeat after me "My safety is number one!" Keep repeating that because when your animal, your kid, your family member is in trouble you'll want to charge in to do something anything! to make it better. ALWAYS remember: If you're injured that makes TWO rescues. If you're not part of the solution you're part of the problem. You COULD die.
Here are a couple of ways you can handle a cast horse. The scene: Your horse is in a stall. His back is toward you and he is lying with his feet against the back wall. He has a few feet of space in front of his nose.
First: Breathe and get grounded. It's not a "new age" thing. When your adrenaline is flowing, the oxygen supply to your brain is slowed. Take a couple of deep, slow breaths and relax your muscles as much as possible. This brings down your energy level and helps your horse relax.
Second: Assess the scene. Do you have room to maneuver around the horse without becoming injured? Is he thrashing and in escape mode? Is he injured? Do you have the tools to help? Get on the phone in your barn (everyone has one, right? ) and call for help. Yes, the time lost could further injure your horse, but your safety is number one. And it's better to have help on its way and have to cancel it, then try to fix the problem and THEN call for help. Do not attempt to help a thrashing horse!
Third: Gather your tools. That means sturdy shoes with traction, gloves, and a HELMET! ! DO NOT TRY THIS WITHOUT A HELMET! You'll need about twenty feet of sturdy rope/webbing/. You need a pike pole/ceiling hook/boat hook/snake tongs. The first two are the same thing and are fire department standard equipment. You should be able to buy them online or talk to your fire department about getting one of theirs.
Do NOT step over your horse and get yourself in between his body and the wall. All work is done from the back. Put a halter and lunge line or long rope on your horse. Pad under his head.
Method 1: Reaching from behind, loop a rope/web around the horse's lower rear fetlock. Pull the rope straight across at a 45 degree angle toward his shoulder. The horse should go over easily. Once he tips past the halfway mark, let go and make sure you are out of his way. The strap will drop off him. He may actually go over on his own once you start flipping him. This is the preferred method.
Method 2: This involves another handy piece of equipment a tow strap. Use two two-ply tow straps abut twenty feet long with a flat loop on each end. You don't want the kind with the twisted loop. It's harder to push a raised loop under a horse. With your pole, push one strap under your horse in the little pocket behind his front legs. When it is through, pull it up over his body. Push the other strap under the little pocket at his "waist" in front of his back legs and pull over his body. Holding both ends of both straps (with multiple people helping) pull the horse backward until he has room to stand up. I don't like this as much because it takes multiple people and can freak out the horse as he is dragged backward. Be sure his down-side eye is protected. It is good if for some reason his legs aren't accessible.
Another thought: Organize your neighborhood so you have someone nearby to call if you need help.