What is the best way to protect my horse's legs during shipping?
Leg protection depends on a few factors - the horse, the distance, and the shipper.
If I am doing my own hauling, short or long distance, I prefer standing wraps for protection, and they keep my older horse's legs from stocking up. Since I am the shipper, I can also make sure they are correctly applied and stay that way. Often times I will add a few quick rounds of masking tape, not duct tape, over the velcro as extra security. Masking tape will break, duct tape will not.
I also like to put front bell boots on. This protects all the surfaces of the hoof as well as the shoe.
If someone else is shipping the horse, I prefer to use velcro shipping boots that cover the hocks. They are easy on and easy off for the handlers, especially if the trip requires lay overs and you can not be there to wrap. Most of the common shipping boots have "built in" bell boots.
This is also up to the horse - and if will he tolerate the hind boots. Some horses will not, and end up kicking to the point of injury or trailer damage. In that case, standing wraps are your best bet.
At one point in time, I incorrectly thought that shipping boots and standing wraps were pointless, and did you really need them to go 12 miles down the road? And then one day I watched a horse calmly unloading from a rig. No leg protection. He calmly and innocently slipped off the side of the ramp, and removed all of the skin and hair from his fetlock to his knee. Save yourself the heartache and certain Veterinary bills by always protecting those legs. It's not just while they are ON the rig - it's the getting on and off.
Some horses like to tempt fate and slide off the sides of ramps or the back edge of the trailer. There is no surer way to have a serious injury.
If your horse decides that shipping boots and standing wraps are not his thing - then you have some training and desensitization to do. It's for his own good, your peace of mind, and your wallet.
Here's some info on wrapping tails, too, just in case you like to do that when shipping.
What works for you?